How many colors graced this wall.
Speaking of budget, there are two Cuban currencies, the national peso called a CUP and the convertible peso called a CUC.
Local citizens are paid mostly in CUP which is worth about 6 cents (according to Alex) compared to a CUC which is tied (pretty much) to the US dollar. So on the street a vendor will be selling a little snack for 1 peso – CUPs to the locals and CUCs to you. If you get some CUPs, in change for example, you are free to spend them at the local rate.
As of now you cannot spend US currency. Bring Canadian or Euro to exchange at the bank.