I patch tubes, but also replace them fairly regularly. I always carry a spare tube. It's a bear to fix a tube during my 3:30 AM commute!

Also, patch kits only last a year in the So Cal heat, so I keep a fresh one in my bag.

I teach the Scouts I take on bike rides how to fix flats too (It's required for Cycling Merit Badge). For many of them, it's the first mechanical repair they ever learn to do!