I have a factory unlocked iPhone 4S that I bought in France. I am coming to visit in California. Will it work on the Verizon network?
Probably not. Verizon (like Sprint) uses CDMA, not GSM. Your phone will probably work on AT&T, T-Mobile, or one of the smaller regional GSM carriers around here. All of the above have prepaid SIM plans available with and without data so you can compare options before you arrive.