I live in this area & I would agree that checking out Northwest Cyclery's route would be a good place to start. You can find the route map online (http://www.northwestcyclingclub.com/...Map%20NWCC.pdf) or I'm sure someone at the shop could help you out.

You might also check w/Bike Barn - located at FM 529 and Hwy 6. From what I understand, they have a route map that starts from that location & takes you around the northwest part of town. I'm not familiar with the route, but I have friends that have ridden it & said it wasn't bad.

I've also ridden from the Target on 290 & Spring Cypress, but we went south on Fry Rd to the high school (where the shoulder ends north of 529) and then we took Horse & Hahl Rd. from Fry all the way out to Katy Hockley Cut-Off. This road (H&H) had very minimal traffic (saw maybe 3 cars in both directions), but a few rough sections of road (old country road). Round trip was approx. 30 miles to do both.