Savannah/SC bike routes???

My girlfriend and I are going to be in Savannah this coming up weekend.  Saturday or Sunday morning I may take the road bike out for a spin.  We're staying at the Westin on Hutchinson Island there at the Georgia/South Carolina border and was looking into some routes.  I'm not wanting a large distance but would like it a mininum of 15miles and max 30 (whole trip).  I'll be riding solo and any route that increases the chances of seeing a gator (the real one not the fans) is a plus.

I found this route on Map my Run but I'm not sure if bicycles are allowed on the large bridge.  It is a US roadway.
http://www.mapmyrun.com/ride/united-states/ga/savannah/677148203

I made this one using google maps but a lot of the route looks like you'd be trapped on a low bridge and I'm not sure how busy the roadway is. 
http://maps.google.com/maps?f=d&source=s_d&saddr=Unknown+road&daddr=32.086738,-81.070518+to:SC-170+Alt+to:SC-170+Alt&hl=en&geocode=Fa2P6QEd570q-w%3B%3BFSYu6wEdQJQr-w%3BFXTQ6wEddrgr-w&mra=dpe&mrcr=0&mrsp=1&sz=16&via=1,2&sll=32.084974,-81.078587&sspn=0.00969,0.019226&ie=UTF8&ll=32.1605,-81.032066&spn=0.154913,0.307617&z=12

I thought about doing a ride to Tybee if I do it Saturday and just have my gf come pick me up on the island since we'll be spending Saturday there.  It'd be a 20mile ride or so but need to know proper routes.

Any other route ideas please share and thanks in advance