You didn't say whether you are local to Kansas City or in what area of KC you are or whether you are just looking for a just-get-me-over-the-party fix or something a little more lasting. I will assume you are local but I will also give you some idea of what to look for anywhere. Chances are that you like to at least tap your feet to a good beat or strum your fingers to it. So forget about the "I can't dance" statement. It is not true. Try instead, "I'm ready for dance lessons." Not only does that give you another attitude it more accurately reflects the truth since every one who already "can dance" took or is taking lessons.
Because your need is immediate rather than a month or two down the line group lessons are out. Group lessons are wonderful for learning and for the pocketbook but they may not happen to be teaching the dance you need now and they take a few weeks of doing before you are as ready as you need.
You need to go for more expensive private lessons, at least a couple of hours worth. You also need any opportunity to practice with someone other than the instructor before the party. Instructors are great coaches but to get the learning down pat you need to dance with a variety of persons, in clubs if possible. You need not-so-predictable partners and music to really make any lessons worthwhile.
Look at my list of dance studios for private lessons and at my list of individual instructors. The dance studio pages include prices (where the studios publish prices). These may not always be accurate - none of my pages is an "official" page for any of the studios and they don't pay me to keep them on my site. They are there because many folks simply need the imformation. When you call, do ask about prices, both from studios and instructors. If they have a lot of jargon about programs and options rather than just prices, especially if they avoid straight-ahead price talk, try somewhere else.
If you are not in the Kansas City area check your local yellow pages. Look for "ballroom" in their ads (you will find a ton of others which teach ballet, jazz and tap, mainly to children).
If you look for a dance studio look for non-contract lessons. I doubt that you wish to sign up for an entire program. Besides, contract studios usually want to get you signed to a next contract and a next before the current one is ended. For those persons who have the money or who want to have such a program then fine. But this can get pretty uncomfortable after awhile.
Do explain that you think you are in the "I can't dance" category and need to learn something as fast as possible which will allow you to function at an upcoming, scheduled, party.
NOW - as far as what you need to learn.
1) rhythm and a sense of confidence in the step (as in "step right out") are more important than the specific step in terms of appearance.
2) Knowing a "step" (a pattern) gives you something to do with your feet so that a) you look capable b) you can dance with another person c) you have a routine you can rely on.
3) listen to the beat - learn what a "downbeat is" and listen for it. It will tell you when to start each step.
For a dance which will allow you to dance competantly in the largest variety of situations, go for swing. If they rattle off a lot of types of swing go for East Coast Swing, or single-time or triple time or Jitterbug or rock. These are all just about the same. They do a "1) step and replace, 2) step and replace and a 3) rock/or/tap/or/back step." West Coast swing, although you can get these very inexpensively at the swing club, is out for any very quick learning. (Interchangeable pattern descriptions: step and replace, one and two, one a two, triple step, etc. The "and" or the "a" in the middle indicates a slight emphasis [or pause, or hesitation or accent - call it what you will] between the end points of two beats, at about the two-thirds to three-quarters point - this is where the music "swings".)
Avoid (for the moment) the other ballroom categories (i.e. foxtrot,
walz, rhumba, etc.). They are wonderful but you really need to focus on
one thing you can get down pretty quickly and which will actually be danceable
to the music you will encounter at the party. Swing can be used for darn
near any music and a few simple swing steps can be learned in short order
which will carry you through a lot of situations from rock, to hip-hop,
to blues, to country to most anything else. As long as the music "swings."
If you are not the leader, and a partner starts "steer wrestling" you around don't dance with that person until they know better. They need lessons. Many people really don't know any better. With some movements you can even be injured. If you don't know this is not good leading you generally feel as if you should have known better how to dance or you just feel a bit beat up and you think dancing is such hard, bruising work. The "steer wrestler" is not a good dancer. Period!
And don't feel you have to dance to everything. Some music just won't fit what you can do right now. It's okay. Gives you a chance to talk, and maybe to savor the moment of realizing that you have been on the floor and your previous group of companions hasn't.
Further: Get yourself into a dance group where you can learn with a
lot of other people and do so inexpensively. Check the group-lesson listings.
These are good safe places with many other dancers (new and experienced)
which offer beginning-level instruction on a regular basis. Spend time
at various clubs with dance floors and danceable music with some of the
dancers you have met. Because the music isn't always as easy to dance to
as the music picked for instruction you will strengthen your dancing abilities
and get more from your lessons.