I pretty much had the same experience at my 5K service with Chula Vista Toyota. They said they don't carry 5W-20 and use 5W-30.

Personal opinion here, I don't really see a big difference between 5W-20 and 5W-30. Both will flow the same when cold, providing equal startup protection.

The main questions in my mind is the durablility of any extra viscosity index improvers in the 5W-30, and how do the HS (High Shear Rate) ratings comapare? I also wonder if 5W-20 increases engine wear?

I found this interesting claim at http://synlube.com/sae5w-20.htm:

You will definitely get better mileage with SAE 5W-20 then SAE 5W-30 oil, but not by much, usually the optimistic estimates are LESS than 1%. The bad news is about 30% reduction in engine life (from 100,000 miles or 10 years to 70,000 miles or 7 years).

Only manufacturers who have 3 years or 36,000 miles powertrain warranties currently recommend SAE 5W-20 oil to be used in their NEW 2000 through 2006 model vehicles (FORD, HONDA).