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.
SPD's will work great in traffic plus you can walk in them too unlike road shoes which you will waddle like a duck and they can be a pain when trying to clip in all the time.
The only downside, at least to mountain SPDs when used on longer rides is that they can create a "hot spot" on the foot after long miles. This happened to me so for longer rides, I use road pedals that offer more surface area for my foot.