I switch back and forth between clipless and double straps all the time. I like both, clipless for long rides and going fast, double straps for going to school and fooling around. The transition is hard only the first few times. Now it's nothing. Clipless is better without a double than double straps to me though as a pedal system (depending on the clipless system too, but I <3 ATAC). I'd suggest doing what I do, save clipless for serious rides, alleycats, whatever, use straps for going to school, the bar, parties, grocery store runs and all that stuff.

It shouldn't take longer than 3 minutes to swap out one pair of pedals for the other.