Best cell phone plan for three month stay in US?

Hello Internet,

I will stay in Houston, TX for three months starting August 2014. Of course my German cell phone provider is useless there because roaming would definitely exceed any budget.

So I was browsing the web (Tmobile, AT&T, Verizon) and I'm kind of lost with plans and coverage and all the stuff and thought why not use the combined knowledge of The Verge?

A little information: As I will only stay in the US for three months, a contract is absolutely not wanted. I own a Nexus 4 so I need a Micro-SIM-Card. I don't think I will use calls or text messages often, but I need mobile internet access. ZIP code is 77070.

It would be really, really great if one of you could help me choose the right plan to go with.

Thanks and kind regards,