Small cities and towns with big city people

So I have a problem. I love being surrounded by diverse, interesting, and intelligent people -- but I hate big cities. A total metro-area population of around 500k seems to be the biggest I can tolerate.

I'm not sure it exists, but are there any areas that are similar in composition/demographics to big cities, but with a lower population? Ideally with a good amount of people in the 25-30 age range, intelligent people, and people with interesting hobbies and unique perspectives on life.

Bonus points for:

• Can buy an acre of land 10-20 minutes of town for relatively cheap
• Hot weather
• Located in a desert
• Access to mountains

I don't care much about good food or politics.

I'd be interested in options in the US or Mexico + Latin America.

Thank you very much!