I am just getting into this as well but I do have an idea for you. Several years ago my brother-in-law had the same problem. What he did was to arrange to have his cart at a fairly busy freeway rest stop. This place was very isolated so the people who stopped were on a long drive and many of them ate. He didn’t get rich but he could depend on making $200 in 4-5 hours.
Maybe this could help you until you find a better spot.
I agree with one of the other writers, perhaps it may help to think outside the city box, at least for a time.