What part of town are you? Houston is pretty spread out, so it may be better to specify a region.
Outdoors is pretty tough, since there are only about 6 hospitable weeks per year in Houston. I did spend some time at a company that officed on the BMC software campus, which I would definitely say was conducive to coding. Downtown, Discovery Green may be worth checking into since you have houstons city wifi available there. Indoors, pretty much every starbucks in town has at least one person working for extended periods. There are a few pubs that are open during the day that have wifi access that could do the trick as well.
