I went to Yucatan Peninsula in November last year. The weather was pretty good. Don't remember any rain in the 2 weeks we were there. And it was pretty warm. I seem to remeber thinking that it would have probably have been better in October ie a bit warmer, but not excessively so.
Probably depends where you go. Mexico is a pretty big place. I imagine that you would get very different weather in the north, compared to the south. You would also get different weather inland compared to the coast.
The following website is quite a good website for climate information:-
http://uk.weather.com/weather/local/MXDF0132?x =0&post=post&letter=M&code=code&y=0
If you click on the above link it will tell you the current weather in Mexico City. There is a 'Climate Statistics' link which will indicate Average Monthly Temperature and Rainfall.
Remember that hurricane season is from 1st June to 30th November. If you have the bad luck to be there when a hurricane hits it will be pretty wet and windy for a few days!!!