drove there several times, including inland to chichen itza Coba and Ek balam . came back from Coba at night...
anyway, never got pulled over, never had an issue at all. just pay attention to the traffic signals/signs!!!
i think most people get into trouble driving there because they don't know where they are going, and because of that, they are not paying attention.

the worst part of driving there , imho, is the simple fact of not knowing where you are going/ not many street signs once you leave town
heck the car rental place we rent from serves you cold beer as your signing the contract. (technically, they were out of beer the last time we were there and gave us tequila instead....just sayin)
good stuff- you'll be fine
(one thing- i ALWAYS carried a copy of my license and passport along with a $20 bill in my front pocket. never had to use it though. better safe than sorry!)