You can get just as good of a work out with
powergrips or toe clips as you can with clipless pedals. I've got powergrips on a couple of my bikes and really like them a lot. I often ride with just normal Teva sandals and powergrips. It is very easy getting out quickly. If you don't care about riding for speed and you'd like to get out easily, try the powergrips. You can also buy them already attached to pedals from Nashbar, but they'll fit to many platform pedals that can often be found at minimal cost.