I am a COMP MSI who is both NWT and did ISAC. Honestly - I highly recommend doing ISAC.... but NOT for the reason you give. You need to know that COMP is on a block system (DO2009 was the first group) and ALL of gross anatomy is done in an intense 8 or 10 weeks. Which means that you will NOT have a lighter load for the rest of the semester - you will have practically no lectures to attend for those 8 weeks if you do ISAC. Now, that doesn't mean those 8 weeks need to go to waste. 1) you still are doing anatomy as a fascilitator, meaning you remember your anatomy much better and 2) you will have time to get ahead on other subjects... and we DO2009's would be more than willing to tell you what to do to get ahead.
Here's the con - you can lost momentum when you don't have to go to lectures for almost 2 months. ISAC is an intense 6 weeks and you meet great people in a very close-knit community - living in the lab with 30 people who are very focused on school. You also will do every dissection - whereas those who don't do ISAC will do every other dissection (which, during the regular school year, is very much a blessing... there's nothing more frustrating than having other exams you are worried about and having to spend 2 hours a day scraping fat before 2 more hours of dissection). So if you get into bad habits of being lazy in those "off" weeks when the rest of the class is doing anatomy, you could be in trouble when they hit the next block and you've gotten used to a nice slow pace.
I don't think there was a single person who regretted doing ISAC this summer - even though some didn't realize it would mean a block of 8 weeks with practically no lecture during the fall, rather than having a little bit lighter load all semester (you'll still have OMM & Essentials of CLinical Medicine as well as a couple other minor things).
As far as Helix goes - it's not best price around and you need to realize that the train is 1 block away and quite loud all night... but that is supposed to stop in July so it may be better. Look at craigslist for apts (inland empire or los angeles sites - Pomona's kind of in between), and Western's banweb has a housing area - both for apts/house and for finding roommates. It's literally across the street from school - which is both a pro & a con... Depends on how much you enjoyed dorm life.
Feel free to shoot me any questions regarding COMP. 🙂