If you were happy with Sprints coverage then any of their resellers should work for you, and they have plenty of MVNOs. Boost, Virgin, ChitChat, Credo, Eco, Expo, good2go, Net10... the list goes on. You are fortunate to be in an area where Sprint actually works. In our market they are pretty horrible.

You could use one unlocked phone and two pre-paid plans and switch between the two (by switching the SIM cards) when needed. The only problem is you can't do that with a CDMA phone unless it is one of the newer smartphones that come unlocked, like the HTC One, or Droid Ultra (both very expensive off contract).

The other solution is to get something like this to boost your signal at the vacation home: Amazon.com: Wireless Extenders zBoost YX545 SOHO Dual-Band Cell Phone Signal Booster for Home and Office up to 2,500 sq. ft. of Coverage: Cell Phones & Accessories

Ok this is a long story. I live in a rural area in Colo with no phones. over the last 8 years I have had Alltel, Verizon and Sprint. Verizon worked fair, Alltel sucked, and Sprint was wonderful, till they kicked me off their network because they said I was ALWAYS roaming. When they did they said I was coming off of AT&T towers. So I went with Trac phone and it works Ok here but not at all at my vacation home in Texas. Tracphone uses the Verizon net work here and my LG86c is supposed to use both 900 and 1400 services. I was considering purchasing an unlocked phone
and switching sim cards when I go to either house but am not sure how well that would work. AT&T does not work here but is the carrier of choice in Texas. Does someone have a simple, not to expensive solution? I don't mind paying for the phone but 2 carriers/service plans?