I don't have proper cycling tights per se, just a pair of base layer tights that I wear under a pair of atheltic shorts. I ditch the tights as soon as I can. This time of year, that means if it's 32-35º F or warmer, they stay home or get stuffed in my panniers, and I wear only shorts. That being said, I probably have much less of a problem w/ road grit than you do; the precipitation which helps to make the grit stick is less frequent here than in the PNW for sure. On days when I do get road grit, I'm likely to be taking a shower at work anyway, and I always shower first thing when I get home (wife's edict), so a little grit doesn't bother me.