I averaged six classes per semester in undergrad, and while I probably still had ample time to study for the LSAT, I surely would never have done that. You can't always tell when your workload will drastically increase or decrease, or a slew of other things.
You are likely asking because you are registering or have registered for your fall load already. The problem is you don't have your syllabi yet and likely won't for months. And even when you get them, they may be subject to unpredictable changes. This is NOT something you want to deal with when studying. Consistency is key.
I studied in undergrad for the LSAT but ended up taking the better part of two years off. The difference in being able to study at my leisure versus having to juggle it among student activities and a full class load (I didn't have a job) is, to be cliche, like night and day.
Plus, you want to be giving your intellectual all to this test, not the leftovers when other obligations permit. Take the five classes, join some extracurricular clubs (Habitat for Humanity, Student Government, Big Brothers Big Sisters, Society of [Your Major] Students, etc etc), and enjoy a full semester that will only add to the quality of your application.
Furthermore, studying for the LSAT during the semester will compete with your class study time. This puts your LSAT score in (in)direct competition with your GPA, the two most important factors in your admissions.
Unless you are currently a 4.0 student and/or have already discovered the formula for straight A's (it took me two years to discover it and a third year to actually master it), I recommend not studying for the LSAT simultaneously.
Also, after having taken the time off from school after undergrad, I highly recommend it to anyone considering it. I spent nearly two years in Korea and I feel like I gained so much from it, from perspective to language and culture to just growing up in general.
If you do decide to take the LSAT though, as others have said, ensure you can commit the necessary time. If taking in October is your goal, speak with the professors who will teach your classes (or if unknown, speak to the program coordinator(s)) and try to find as much information as possible about these classes. Also, ask students currently in these classes now, or sit in on them if you have time. It's April, and there's a good chance that at least some of what you're taking in the fall is being offered right now.
Get as much access to the information as you can to hash out a schedule that balances the necessary study time for the LSAT with the necessary study time to make A's in these classes. And unlike in other semesters, cramming for midterms likely won't be an option as Davidbentley said. So if your style is to load up on study hours the week before rather than consistently review during the semester (I'm of the former), you need to consider the likelihood that you will actually be able to make these changes to yourself.
Best of luck in whatever you decide!