Craig,
Wow, you picked the hottest time of year to visit Houston! Even so I'm sure you'll find our city full of friendly people with tons of things to do. (And yes, we have our share of tall men here — I happen to be one of them

.)
A few suggestions. I've limited the list to Marriott and Hilton properties since you expressed an interest in those, but other major chains are available in these areas. None of these are in Montrose (there aren't any chain hotels in Montrose) but all are within a 10 minute drive most times of day.
Downtown- Marriott Courtyard — Brand new, in a historic building on Main St., right on the new MetroRail line at the Main St. Square station
- Marriott Residence Inn — In the same building as the Courtyard, also brand new
- Hilton Americas — Gorgeous new Hilton property adjacent to the George R. Brown Convention Center, very modern
- Doubletree Allen Center — An older property; don't know much about it but it is downtown and slightly closer to Montrose than the others (but only by a few blocks)
Uptown/Galleria- Marriott Courtyard — On the 610 West Loop, just south of Westheimer and north of Richmond
- Fairfield Inn — On the 610 West Loop, next to the Courtyard
- JW Marriott — On Westheimer, directly across the street from The Galleria
- Marriott — On the 610 West Loop at San Felipe
- Doubltree Post Oak — An older property; have heard the Guest Suites a few blocks away is nicer
- Doubletree Guest Suites — Close to the Galleria off Yorktown between Westheimer and West Alabama
Another option that's closer to Montrose is the Holiday Inn Select on the Southwest Freeway between Kirby and Buffalo Speedway. I have not stayed here but my company did use their conference facilities a few years ago and the public areas appeared to be pretty nice; certainly a cut above most Holiday Inns. The building is a high rise and appears to have been well maintained and possibly recently renovated at the time we met there. Also in Greenway Plaza is the Renaissance. This is an older hotel and I really know very little about it but it is a Marriott property that's not too far to Montrose and closer than the Uptown/Galleria properties.
My top choices would be either of the Marriott downtown properties or the Hilton Americas. The Hilton is very nice but a little farther from the action; the Marriott properties are in an interesting historic building and being close to MetroRail would allow you to be able to hop the train north to Preston Station to the downtown club/restaurant district and theatres. Southbound will take you to the Museum District Station (art, natural science, health science, and Holocaust museums nearby) as well as Hermann Park, the zoo, Miller Outdoor Theatre and Rice University. And you'd still be within a short drive to the gay bars/clubs/restaurants in Montrose and Midtown.
Hope this helps! If you want suggestions on places to go/things to see/restaurants/etc., feel free to e-mail me or send me a private message on FlyerTalk.
Steven