@kjarrett on the recommendation of a co-worker years ago, I started using sun sleeves/legs. They are noticeably hotter (emphasis on noticeably...that is: not detrimentally) when it is humid, but I haven't suffered from bad chigger/tick bites in years. One or two might get through, but it's nice to be able to give a quick brush and get 99% of them.
IMO, long, unkempt grass is more detrimental to the derailleur than you. I usually ride the single speed through Brisbane/etc during the 'off' season, and the handful of times I haven't have resulted in derailleur damage.