Please try to consolidate your porting questions into one discussion, vs. peanut-buttering them around in separate posts.
Any US mobile carrier can be used. We usually see the best results with AT&T GoPhone and T-Mobile prepaid, and the absolute worst results from the America Movil family of brands (Tracfone, Net10, SIMple Mobile, Straight Talk and Page Plus), and the very bottom of the barrel is H20 Wireless.
The reason nobody mentions Verizon is that you wouldn't want to establish a 2-year contract with them, and turn around and port it out -- you'd incur a huge early termination fee. It would need to be a prepaid number, or a postpaid number that has already satisfied its contract term.