I had the remnants of a terrible cold when I went out on New Year's Day for the Icicle Bicycle Ride here in Pittsburgh. The cold was absolutely the worst I have had in years for both longevity and severity, with a running nose and cough that lasted for a month. I didn't want to miss the ride, even though the weather was pretty cold (24 degrees with a wind chill of 11 - coldest I'd ever ridden). I got about 5 miles into it and realized that I just didn't have the lungs for the pace we were riding and my nose had turned into a snot factory running at 110% of capacity! I baled on the ride at that point - probably should have just slowed down and continued, but my toes were starting to get to me, too.

I've ridden through other colds with no problem in warmer weather, so if I were you and the temps are in the 50's as you've said, I'd go for it. Especially if you've been cooped up and are suffering from cabin fever.