The 2012 Olympics will be Summer Games. Therefore my criticisms are based on summer and fall season situations.
Houston -- too hot, humid and buggy for a good venue
Dallas -- maybe OK
Cincinnati -- Hey I'm from Ohio; I could deal with that! We might even have some of the venues up here in Cleveland
New York -- (I assume you're talking about New York City) too crowded already, no room to build an Olympic park or village unless it's actually out on Long Island, in New Jersey, or at least an hour upstate in the Catskills or Taconic Mts. Remember, Lake Placid NY already had two Winter Games (1932? and 1980)
Los Angeles -- same as New York, and L.A.'s already had the Olympics twice (1932? and 1984)
Tampa/Orlando -- Some of the venues for the 2000 (Atlanta) Games were there. I think they still have room to build venues, but there would be a lot of controversy over spoilage of environment during construction (remember the Kissimmee River! It was destroyed by culverting/diversion during the buildup of the area!). It's already crowded by tourists so I don't know how much more headache the area could take.
Washington/Baltimore -- believe it or not, some of the 2000 (Atlanta) Games venues were this far north! I'm not sure the Federal Government would be happy with the influx of foreigners in the area given security concerns.
There are some beautiful areas in Virginia and Maryland which would make great venues, if they aren't spoiled in the process of construction. Could you imagine white-water kayaking, canoeing, and crew on the Potomac and Cumberland Rivers?
San Francisco -- might be nice
Buffalo, NY/Niagara Falls, ON (a true International Olympics) -- just a really nice location. Already has good hotel facilities.
Minneapolis, MN -- why not the Northern tier? Lots of lakes for water sports. Location of Northwest Airlines's hub, would be easy to reach for Asian and European athletes, via Northwest and KLM.
Kansas City, MO -- why not the Midwest? During the early fall the threat of bad weather lessens. Besides, KCMO is not really in Tornado Alley.
Albuquerque, NM -- why not the Southwest? "Dry heat" in the early fall, not bad weather (what weather?). Sandia Mountains and Rockies within short distance. Water sports could be held at the University of New Mexico and on the Rio Grande (which would give NM good reason to clean up the river!)