I live in Dallas and use the one downtown the most.
here is a map of all the 24 hour fitness locations in the Dallas area you can use with the costco deal. You pay the 350 up front to costco and then take the certificate to 24 hour fitness and they do the deal. I have used them in Austin, Houston, all over DFW, and Ft. Collins, CO. You can use any level lower than the "Super Sport" clubs, which most are below that level, in the country. Most of the ones I have been to are open 24 hours during the week, but some are only open until 8 or 9 on fri, sat, sun. There are some that are 24/7/and almost 365. The website will tell you the hours, they also have an app with all that info.
Link to the "find a club" page.
http://www.24hourfitness.com/health_...teractive.html