I need to learn numbers. I can confidently state there are at least 2 numeric systems: one for counting, and one used with money.
On the whole, I have stayed away from street venders (food or otherwise) because I am unable to understand the amount due or suggested (haggling is normal). Stores are safe, because a price is listed and a register produces something visible.
Not being understood isn’t what bothers me, it’s that I would probably just hold up a bill and am worried the seller would take the whole amount, sensing my ineptitude to know the difference.
edit: there are 3. Another system for ordering.