Road riding for exercise is heavily male-dominated here, and being lighter than most of these guys I tend to do well on hills (though I suck majorly on the flats). But when passing someone on a hill I never know if they're on their first or 5th lap, or if they've ridden 80 miles just to get here, or if it's the day after a race or whatever. So if anything I settle for a brief, friendly smile, or maybe an exasperated "d*mn I hate this hill!", or sometimes "did you know I've been chasing you for miles!" if the guy is cute and I'm up to it