Switch to SPDs.

Traffic is the last place I want to have my feet slipping off the pedals, or to be wobbling around looking at my feet while I fuss with toe clips, cages, or straps.

I've got about 25,000 miles on SPDs in traffic on my commuters. Liked it so much, I have SPDs on all four of my bikes now. I'm always clipped-in the the first half-rotation of the crank. There's no apparent downside when I'm out on club rides. Better still, I can walk when I stop on the way for errands, and the three flights of stairs to/from my apartment are also trouble-free.

For the record, there are 47 stoplights or stop signs in my 9-mile round-trip commute, roughly five a mile or one every 1,000 feet.

I use the single-sided A-520 road/touring SPD pedal. After the bearings are broken-in (500-700 miles), they always flop to the right position to clip-in without even thinking about it. I seem to get about 10,000 miles on a pair before the spindle bearings get sloppy. They're $35 or so if you shop carefully, so I'm not upset when it comes time to replace them.