Yes, they certainly can. Friends and family can donate to your campaign from all over the world using a major credit or debit card.
When they make their donation, they'll be given the option to select their country. This will generate the appropriate State/Country/etc. options for their credit card information.
Important: Your donations will always come to you in your campaign's currency. Your donor's bank will automatically convert their payment into the currency they use, and charge them the appropriate amount.
We do not charge any conversion fees, but your donors may want to check with their bank to see if they charge a currency conversion fee.