DEET (if it's borderline bad for you it has to work), long sleeves, pants, and start a fire and sit/stand near the smoke- fire ban permitting of course.
http://www.amazon.com/Repel-Insect-R.../dp/B004H89KFC
And stop stressing about the things mosquitos can spread. Before moving to Colorado I was bitten approximatley 776,122 times and did not contract anything. I'd worry more about lighting in Colorado.