What dances you pursue depends on what you see yourself doing with your dancing. If you want to do competition or show dancing, or anything along the lines of what you see them doing on the TV shows these days, your choices would be very different than if you're learning for an upcoming wedding.
If you're not sure what you want yet, the "sampler platter" isn't a bad approach, as it establishes a good foundation all around, and gives you time to try a little of everything before committing to one particular style or another.
Assuming your goals are socially oriented (weddings, nightclubs, etc), I would opt for a mixture of dances that include some basic ballroom & Latin, but that also include today's popular styles, such as Salsa, Swing, and Argentine Tango.
Your AM friends are going to push for at least the "main 6" dances in their book: Waltz, Tango, Foxtrot, Cha Cha, Rumba, and EC Swing. This isn't a bad set to start with, as it establishes a good technical foundation. All of them are relevant to social dancing, with the possible exception of Tango, which you won't do much of in today's social scene. I would probably ditch that one in favor of authentic Argentine Tango, and then add Salsa, and perhaps one more Swing style later on (either WC Swing or Lindy).
A lot of this depends on how much time you expect to put into your dancing on a weekly basis. With only one lesson a week and no additional activities (individual practice, practice parties, etc), you might want to scale back to just the essentials -- no more than 3 or 4 dances to start, and only the most relevant to your goals. With two lessons a week, or with one lesson combined with another 1-2 hours of other activities, you can afford to spread things out a bit more.
After about two months, you'll probably begin to figure out what you like and what you want to do with it, and the choices may change. But this is a good way to start. PS -- if you're in Europe or Australia ignore everything I've said, dicth AM and go to a school that will teach you International style.
The discussion will essentially be a sales pitch, so be prepared for that. There's nothing wrong with that... They have a product they want you to buy, and they're going to do their best to convince you it's worth the money. But just like when you buy a car, you need to understand this fact and be prepared for it.
I'm actually a supporter of the chain schools, and I think they play a very important role in the ballroom dance community. There are certain types of students for whom I think they are the perfect solution. So I'm not going to tell you not to buy lessons from them. They might be just right for you. Just realize that you do pay a premium for them, so you shouldn't buy the lessons unless you have carefully considered your options, and have decided that they are just right for you.
Remember during the sales pitch that you are not obligated to purchase lessons on the spot. You can give it some thought and come back later if need be. No matter what they tell you in the office, no matter what incentives they give you for buying lessons on the spot, you can always come back later if you're not 100% sure you want the product. And they'll still give you the same "deal".
The other thing you can count on is a pitch for more lessons that you had expected. They'll talk about purchasing blocks of 20, 30, even 100 lessons at a time (depending on what the laws allow in your state). A lot of people buy more than one lesson at a time -- perhaps 5 or 10, just to make accounting simpler. But more than that is excessive, and totally unneccessary. So if they give you the pitch about needing to "plan" more lessons, just tell them "Great. Plan 100 lessons, and I'll buy 4 of them now". There's no justifiable reason to enter into a contract for more.
One more thing: If AM is not the perfect solution for you, make sure you ultimately tell them "no" because you've found a better solution. Do the research and find a studio that is right nor you. Otherwise you will have given up a dream or a hobby you wanted to pursue simply because the price wasn't right. The only reason you should quit dancing is because you've decided you don't want to dance anymore.
I hope this helps. Good luck and happy dancing!
Sincerely,
Jonathan