How often you should water depends on your expectations. If you want a nice green grass all summer, then it doesn't much matter what kind of grass you grow -- it will all need regular water to survive Texas conditions and stay green. Provided you can water regularly, bermuda may be about as good as anything. Buffalograss is tougher, but not quite as nice looking. Either of those choices should work. They both go dormant in winter, but only bermuda can be overseeded in winter (if that's what you want to do).
Seeding is probably better done earlier in the season -- mid/late spring. You could do it now, but watering EVERY day is a must.