Using cooking oil is a good alternative, but it can't be widespread. You have to make a deal with a number of restaurants to give you their old cooking oil. A band that my dad worked with had a van that ran on cooking oil. When it drove it smelled of cheeseburgers.
Diesel here in LA is about $6 and most premium gas is around $5.00. Regular is about $4.60. This has given me even more incentive to put off learning how to drive.