I don't work out when I have a bug (cold/flu), but I work around injuries. I had a 6-month battle with a tendon problem in my left wrist from last December until June, and I couldn't bench press. But I was able to do everything else, and I used the pec deck in stead of benching, which seemed to compensate and I didn't fall back.
As far as routine rest; I've found that 1 day on/2 days off is best for me on bulking, although I work my abs 365 days/year without rest. Once in awhile, my work schedule sometimes forces me to stay out of the weight room for up to 10 days, but I still do whatever I can to keep from losing momentum (pushups with my wife sitting on my shoulders, etc) . I commute from Dallas to LA several times a year, and I usually drive, so I try to get in sync so that the 2 days on the road aren't workouts missed. My Dallas weight room is only an Olympic set & bench, and a 25-85-lb hex db set. I can keep up there, but I would join a gym or add to my weight room there, if I were to stay for more than a month or so at a time. Usually it's 3 or 4 weeks there, and 3 months in SoCal.
Charles