Have been going to Gambia for nearly 14 years now and due to go again in February 07. I think to really enjoy the atmosphere, and different culture and get out into the markets, and experience different restaurants not tied to one hotel should be shared as it is much more fun.
However, if you are desparate for a holiday and must go it alone this time, I would say yes, it is safe. Just find a decent guide and/or taxi driver who is not too young, and act as if you have been going their to see friends all your life and it will be a doddle.
It's the same old story, if you wear shorts up to your armpits and cleavage heaving in the sun dripping in gold etc. etc. then you will attract the obvious.
As far as only wanting residency in this country, come on, they all have a go. This is how we started our 'mission'
Our sponsored lad is now 30 has a wife and son who he has named after my husband. We clubbed together here with friends had car boot sales etc. etc. bought them a plot of land, and then enough to build a house. His whole family and I mean whole (about 30 ) of them live there now complete with garden and welland he has managed to secure a job because instead of offering to bring him over here we paid for him to go on a computer course in Serrekunda. So please don't tar them all with the same brush.
It can be a magical place (poor man's Barbados) or a nightmare
if you dont take the right precautions which when you think about it are all common sense.
Go for it, have a great time.
Incidentally who are you going with, as First Choice work out much cheaper than Gambia Experience.
We have always stayed at the same hotel, but this year are trying a smaller one run and owned by an African family. But I would as the other respondee said, go for a bigger hotel in the middle so that you have more chance of meeting others and more trips etc. etc.