aztimm

Depending on where you are staying, you can actually get out and go to a pool suited to actually swimming laps.
There's tons of good pools throughout the area, including several 50m pools. For instance, Scottsdale has 3 city pools, open to the public with very generous lap hours, for $3 per visit. Cactus pool is at Scottsdale Rd/Cactus, and is sometimes setup 50m (otherwise usually 25 yard).
Or if you'd rather, there are several masters swim groups around the area, which you could drop in with as a visitor (usually for free).
Even when it is warm, many of these pools use aerators to try to keep the water at a reasonable temperature.

I was at a conference at the JW Marriott Desert Ridge earlier this year, where I actually stayed there. Their spa has a 25m lap pool, but it was kept at such a warm temperature (when it wasn't really that warm out yet), where it was difficult to do much more than float.

I swim with the masters group in Mesa, and have swum in many of the pools throughout the area. Personally, I'd pick a hotel based on other perks, and just go off-property to swim. Let me know if you'd like more specific info.