I will definitely use the public transportation if it is convenient for me-- however I will still need a car to get to a remote area where there is no transportation connected there to here (e.g. national parks, deserts etc in Southern California).
But it will be NICE to not drive all the times! Maybe 20% of the times I will use my car whilst the rest will be toward to use the public transportation. I will LOVE that-- that way I can read my book et cetera-- being more productive with my time rather than using my eyes to WATCH where I go on the freeways.
It is hard to use public transportation because there are unpredictable happenings such as a bus breaking down, late bus drivers, delayed subway, et cetera that just eats away your time... not a good thing when you gotta show up on time for work!
While travelling in other countries, I try to use their public transportation-- Paris, London, and Barcelona got pretty good system and it takes you ANYWHERE you wish. Sweet! Italy, in my experience, is better by being a pedestrian-- their cities are not widespread like American cities so it is easier to walk around (or occassionally use their bus system).
San Diego has a notoriously poor public transportation. We do have a trolley system (similar to subway but ABOVE ground... similar to train but SMALLER), but we are still fixing it to make it accessible to all over the county (right now, the south and central part of county get the best-- north and east county are left out of the loop). Buses are the most reliable transportation, however when it comes to rush hour-- forget it. It will take me two hours to get to Chula Vista from Central San Diego via bus/trolley while it only takes me 20 minutes to drive in my own car. You see the pros and cons we gotta weight?
What a bummer but, hopefully in 10 years or so I will be able to use some of San Diego's public transportation to my future work from my home.