Darcy, the trolley tour is actually a bus designed to look like an open air trolley car. It does have narration.
The trolley system, however, is not narrated but a fun way to see the city and make some great stops -- all on the cheap.
I would opt for the trolley and head to Old Town for shopping, sight-seeing and lunch. You mentioned the day pass, or you may also do one to just that stop. Tickets are at the trains tation one block from the port.
Here is a link to the article I wrote about San Diego and things you can do. It's a very easy port to do on your own.