Hi Jim,
You won’t be able to open a bank account on a tourist visa under your personal name. But you would be able to form a corporation (you need an attorney/notary in Costa Rica for this) with you as the “officer/president” and open an account in the name of the corporation. It would essentially work like any bank account, with wire transfers, debit cards, etc. available.
As a temporary resident, with the pensionado (retiree) program, for example, you will have no problem opening a bank account as either an individual or for a corporation.
As far as buying a car, your best bet if won’t have a bank account at the time of purchase is to go to the bank teller and ask for a cash advance using your debit card. This will allow you to withdraw $1,000 to $2,000 (depend on each bank’s specific policy and your U.S. banks rules) a day from your account back in the states. There is a small surcharge. It’s not ideal. But you could do that for a few days until you have the cash you need for the car. Many sellers will take dollars, by the way.