Does a 50 amp motor home have to have 50 amps?

I greatly hope someone who has had personal experience with this comes to answer your question, but until they do I'm giving you my guesses.

I think the problem will be the physical connection. I don't think you can physically connect your 50 amp male connector to the park's 30 amp female. That said, 50 amp service provides 220 volts. It's my understanding the the other 110 leg (that creates the 220) is only used to power a second air conditioner and also your 220 electric range/oven if you have one. If you don't have an 220 kitchen and don't need the second AC you can run your RV off a 30 amp service.

To do this I think you will have to have someone who knows what they're doing wire a 50 amp to 30 amp adapter cable. I guess I'm kind of surprised 50 amp RVs don't come with a 30 amp adapter cable and instructions on how it can be used, but I don't own an RV so all this could be wrong.