Yes. An unlocked phone will work with any GSM compatible carrier abroad. GSM carriers make up about 93% of all wireless carriers internationally, so you shouldn’t have any problems locating one in the country of your destination.
Please note: in some cases, you may only be able to receive 3G data when in a foreign country. 3G is a bit older than the most recent wireless network technologies and so is a bit slower too. LTE, which is the current standard, isn’t available everywhere yet. If you’re so inclined to read about why, we recommend this article.