Gambia:
Might be worth researching the political situation nearer the time, I think it is a bit unstable at the moment. Travellers, as a source of income, are usually well looked after though.
I recall seeing some rather robust policing methods. Avoid any contact with soldiers.
Every village will have its bustling incredibly noisy market (normal conversational volume is about 9/10). Chunks of meat hang, literally covered in flies. Speaking of flies, the Gambia has flies like I've never seen before - but then I am not all that well travelled - you can stop for a minute, no flies, 30 seconds later there is a fly, 30 seconds later you are being devoured by insects that do not seem to care whether they live or die. Starving flies.
I did not, however, have any belly woe in either country - take the usual precautions with uncooked food and water sources - and be careful with ice. In fact, avoid ice unless it is from a big hotel or somewhere you can rely on the source of water.
Food is decent enough - one of the best places to find cheap eats was to find where the taxis park in the larger villages - there would always be a little tin hut or something nearby where the taxi drivers would eat. Lots of nice fish (I was generally near the coast) butterfish and others I have not had before, plus rice and cheap-ish fruit. Bottled water readily available.
Watch the sun: it was always overcast with heavy looking cloud out there but this did not prevent me being burnt to cinder to begin with.
In the Gambia you'll be seen as a nutter for cycling anything other than a short distance. Out of the bigger towns, you'll be quite an event. Kids will shout "toubab, toubab" and before long you'll have a gathering just staring at you. Get used to it. The locals are always friendly but may be a bit shy. Be careful taking photos - ask permission - for instance, taking photos of a market scene in which you inadvertently include women can go down badly.
In the bigger towns, near hotels, you'll be accosted by people trying to get you to go to this or that restaurant or bar, and will happily attempt arrange a liason with their "sister". These guys can be right pain in the arse and you need to be forthright from the off. Friendly, but a firm no. Most of them are not Gambians but are from Nigeria or Sierra Leone etc.
More in a bit. Must dig out some photos.
Another thought: if you fly to The Gambia, you'll be pounced on on arrival by various characters all claiming to be this or that. They can be very convincing. Basically they are just touts operating for various hotels, taxi drivers, etc. Keep a hold of your luggage or it will be whisked off somewhere by someone who will convincingly claim to have been waiting there just for you.
