One consideration may be where you'll end up working. Does your boyfriend have a job in Green Cove Springs already? Or someplace not too far such as Orange Park? Where do you think you might be working?
You might find some retail or restaurant work in Fleming Island/Green Cove or in your next closest location, Orange Park. For higher-paying work, you'd most likely have to commute across the river to Jacksonville.
40 minutes to UNF sounds a little too optimistic from Green Cove Springs, I would plan on closer to an hour. You'll need to travel through 3 counties and cross one major river - from Clay county, through St. John's county and into Duval county and cross the St. John's river - that's quite a bit of distance with plenty of potential traffic snags.
Have you considered UF in Gainesville? If you're looking for a more rural lifestyle you can live just on the edge of Gainesville and have an easy commute in to school. Gainesville is a hip little small town

.