It's summer time. The days are hot, the sun is out, and you're relaxing by the pool... stressing about all the homework you have due soon (if you're not on your laptop doing it by the pool already). What you originally thought might be a great decision, turns out to be the exact opposite.
Now I'm not saying this is everyone's perspective of it, but I also know it's a view shared by many. At first it may seem like a great idea; only one or two classes after an entire semester of eighteen or so credit hours? Perfect! Unless you're the type who takes the summer to rejuvenate yourself-- which you should. Your body needs a break. If you're constantly stressing about school during the academic year, give your mind a rest during the summer. Unless, you absolutely need to take summer classes. Then that's a different story.
So here's my advice to you. If you want to further your college career quicker, or only have a few credit hours left of your degree, take them. If you want a summer but still want to further your education quicker, take online classes. However, if you know you're going to want the summer to yourself and to travel, either get yourself strong portable Wi-Fi or just don't take them at all. Time management is harder during the summer than during the academic year. During the academic year, your mind is focused on everything school related, so time management comes easier. However, during the summer your mind is in a different mindset. Your brain wants a break from the stress you just put it through during the academic year. Suddenly Netflix and sleep seem all the more enticing. Summer classes also move at a much faster rate than regular session classes do during the academic year so prepare for that.
Take advantage of the summer time you have off, because you won't have that forever. Soon, you will be completely in the real world and there will be no such thing as 'summer vacation', so take advantage of it while you can and do all those things you want to do -- or can afford. That, you won't regret.