As far as your credit/debit card goes I would suggest buying a travel Visa card rather than using your own credit card. You purchase the card and put whatever amount you like on it in whatever currency you want. Then the purchase amount is simply subtracted every time you buy something. It is easier than taking traveller's cheques and safer than carrying your own personal credit card around. Here in Canada we can purchase them at any Canada Post outlet or through a bank. When you buy it there is a $15 activation fee. They give you a temporary card until the permanent one arrives in the mail. It takes about a week. If you do decide to just use your own card be sure to call the company before you leave to let them know you are travelling and will be using it abroad so that the card doesn't get flagged once you start making purchases.
Regarding your cell phone. I would suggest getting a disposable/burner phone for your trip and using prepaid time cards otherwise you will come home to a phone bill that is through the roof because of the international roaming charges. I also just found out that you can also rent cell phones over the internet. Yes, I thought it sounded weird, too, but a friend of mine did just that for his last trip. He said it is much cheaper than buying a disposable one. You choose the one you want (they have all kinds, including smart phones), they mail it to you, and then when you return you mail it back.
Good luck and Bon Voyage!
Currently planning a trip to Europe.