I absolutely love Savannah, we used to live about 2 hours away and went all of the time. We actually got married in one of the squares and named our little girl savannah, so yeah, we love it. Stay in the historic district, NOT mid town! I know it looks really close on a map...it's not. It will easily take you 30 minutes. Does savannah have a lot of crime....yes. Really any direction you go from the historic district gets bad very quick. I will say in the past 10 years those areas have gotten much better but it's still there. We've stayed a ton of places, in the fall or winter I like the B&Bs in the summer I prefer the Andaz (prefect location and it has a pool!).
I can't recommend the Savannah Taste Experience tours enough. They're both great.
For food, stay off of river street, very over priced. We love love love Crystal Beer Parlor, Jazz'd tapas, Garibaldis and you can't miss Mrs. Wilkes Boarding House. Skip Paula Deans.....it's not bad, just not worth the wait and definitely not what it used to be.
I could talk all day about Savannah and Tybee is super cute, you feel like you've stepped back into the 1950s. It makes for a great day trip. Or Hilton Head of you've never been.