Interesting situation you have. I'm the type of guy that would take the long route especially once I worked up to it. I would say that until you can work up to doing the 11.8 miles without having to park your car some where stay with that route; then when you can do the entire route without difficulty then switch to the 17 mile route.

I noted you are a female, do you have a cell phone and does it work along those routes? The other thing to realize too that if you don't dress too revealing must cars buzzing past you (especially when it gets dark) will think your a male because they don't expect females to be out riding at that time.

If you end up riding when it's dark do yourself a big favor and light yourself up like a Christmas tree! If you don't have an adequate lighting system for the whole bike and money is an issue, you can get a decent lighting system (front and rear) for $100 to $140 depending on front lighting power. My 13watt headlight cost $48; combine that front light with a flasher to attract attention from Vistalite for about $12; Cateye TLLD600 taillight with 5LEDS mounted vertically will provide a huge amount of side and rear light for about $20; barend lights about $15; reflective leg bands about $5 and your at $100.