I'm the guy at UMN who is from LA originally. I went to the UCLA flyout last year and I really was not impressed. No one seemed enthusiastic about the program at all. Did you attend either flyout?
I really would not let the rumored mathematical rigor of UMN's program worry you too much. I had never seen any concepts from real analysis before I came here, and between math camp and the analysis class I'm taking now, I have had no trouble at all with the math.
The weather should also not be a big concern for you. For one, you will be inside most of the time anyway studying. If anything, the cold weather disincentivizes leaving the office which makes you work more. Second, our weather is exaggerated just like the mathematical difficulty of our program. I was among a pretty big group of people who rode their bikes to school every day, even when it was -15 F. It's really not a big deal when you get used to it.