you want the salad, just get the tostada and request a flour tortilla instead of the hard corn shell. You end up with literally the same thing as the salad, but slightly less tortilla and slightly less dressing. Save yourself about $2.
Also, if you have children, take advantage of the free nino quesadillas. Buy a side of their favorite meat to add some protein. One side of meat is enough for three kids to share and change their cheese quesadillas into legit meat quesadillas on the cheap.