A taxi will run you a fortune. As much as you do not want to rent a car, that is the best, and cheapest way. I am not even sure you can catch a taxi to get back from SFMM easily.
It is an easy drive from Burbank...the 5 is right there, and SFMM is off of the 5. Depending on traffic, it is usually a half an hour or so.
I am going tomorrow as well. First time going solo. Hoping for light crowds, and knock out 15-20 rides and take off before the fright fest crowds arrive.