Would a Samsung Galaxy Tab (with AT&T monthly data plan) work for data (Internet connection, Web browsing, e-mail, etc.) and text messaging, from other countries (assuming I have an AT&T international data and text messaging plan?
Yes, you can use international data and text with or without plan but either way it will be $$$$. The cheapest way is to SIM-unlock the tab and buy a local SIM card. You can also just use wi-fi only without any data charges.