Am I better off converting American dollars to Canadian before crossing the Canadian border or after?

see if your bank can do it. pardon the term, but casinos rape you on the exchange rate.

You are better to go to a "bank" in Canada. Some bridges at the Canadian Border offer Banks. DO NOT GO TO AN EXCHANGE BOOTH IN OR OUT OF THE DUTY FREE SHOPS. You will get screwed. The casino will also exchange for you at a fair rate of exchange. They offer this as a service not as a business so they are fair. Foreign Exchange booths can only exist to make a profit on the exchange. I know several bridges have "Royal Bank Outlets" including the Queenston/Lewiston Bridge in the Niagara Area.

Use your bank card to access your US bank account from any Canadian Bank machine. This is the best rate, as it is just a transfer of electronic numbers. No foreign currency inventory is held anywhere, no extra employees need to be paid. This is also safer as you can take out money as you need it, instead of traveling with your whole vacation budget on you in cash. A machine (ATM) at a bank is usually the safest with the least amount of charges. But even using the ATM at the casino is better than hitting an exchange booth.

Go to your bank and exchange it. Trust me I have to change Cdn to AMer every week and it is much cheaper and easier to do it at your own banking institution.

Just do it before hand. That's what I do when I cross over to the U.S. That way it's done.

Today, unless you have one of the very few remaining credit cards that still does not charge a 3% conversion fee, the best rate is from buying $CDN travelers cheques in the USA. AAA (for members) and a few banks charge nothing, otherwise the fee is 1%.