We learn: "Those traveling during the day are exempt from the sukkah during the day but are obligated at night." The halachic states: "This applies specifically when they are able to find a sukkah. However, if they cannot find one, they may continue their journey even though they will not sit in a sukkah, neither by day nor by night." (This refers to one traveling for personal reasons. One traveling for the sake of a mitzvah is exempt even from making an effort to find a sukkah.) In truth, however, one should not go on a recreational trip, when it is not for the sake of a mitzvah or another essential need, if it is known in advance that there will be no sukkah available.
Our Sages said that a person is exempt from the sukkah only when remaining there causes him discomfort (mitzta'er), not simply when it is more convenient for him to remain outside. Furthermore, our Sages said that there may be kitrug (accusation) on one who seeks a way to exempt himself from the obligation of a positive mitzvah, even when the exemption is technically valid.
Nowadays, there are tourist sites throughout Israel that have sukkot. Their kashrut should be checked, since some sukkot are not constructed according to halachah. With a little advance planning, a trip can generally be arranged so that there will be no need to eat outside a sukkah.
Adapted from Sichat HaShevua