Last year we stayed within walking distance and we are doing the same this year. The first year we drove and it was convenient however I think you have to pay for parking. Does your hotel have a bus that goes to the convention center? That might be nice too if they do but I wouldn't take the city bus, or a taxi. Paying for parking will be similar in price and probably more convenient.
I thought taking our own car would be a nightmare but now I feel better about it. Our hotel says it's only 1 block from the convention center and if they have a shuttle they keep it quiet (they sell us tickets to the city bus to get to Disneyland). I'll hope we don't get lost trying to find the parking! Thanks for your help!
I drove to the last two conventions and parked in the garage to the right of the convention center (part of the convention center). Parking was pretty easy to find (signs everywhere directing you to it) and wasn't full when we got there. Like Dinglehopper said it is pricey though. Still I am planning to do it again.
The Toy Story lot doesn't open till an hour before the park. So that would be 7am. If you want to be there earlier than that, then you might want to find another alternative.
I was thinking of doing the same thing. But from what I've seen on other links, people are planning on lining up at 5am.