SihanoukVille's not really a walking town.  If you're downtown and want to go to the beach, you can head off in most any direction walking for a half hour or more and you'll end up at the beach...... And if you're at the beach, you're going to want to go downtown or to a different beach as some point as well.

The main forms of transport in SihanoukVille are: walking, bicycling, electric bikes, motorcycle taxi, tuk tuk taxi, renting your own motorcycle, and car or van (with driver).

New regulations here, require foreigners to have Cambodian driver's licenses for all types of gas powered vehicles.  It takes a month to get a license, costs $40+, and has some other paperwork requirements.  A few places still rent motorcycles, and if you don't have a Cambodian driver's license, you should check with the company renting it to you to find out their policies if the police confiscate your rented motorcycle.  You will be required to leave your passport as insurance that you will return the motorcycle, so watch out.

Headed to Phnom Penh

Walking is easy.  You do, however, want to have a hat or some sun protection in the day. Bottled water is sold everywhere you could possibly go, for about 15 cents for a litre.
Electric Bicycles are now common here, and cost around $4/day to rent.
Motorcycle taxis and Tuk Tuks (carts pulled by motorcycle) are on every street in town. Prices range from 25 cents for a quick ride on the back of a motorcycle, to $10 for 4 people in a Tuk Tuk to go from on side of town to the other.   Prices go up for more than one person in(on) a vehicle, and the later at night it is, the more the price is.

Tuk Tuks in front of Orchidee guesthouse

Cars with driver can be rented for a short trip around town for about $6, and $35 for the day, if not going too far out of town.

Boats are used to get to and from the Islands, and out to sea for fishing, snorkeling, and scuba diving.  Many establishments have a $15 trip to the islands, including pickup and return from your guesthouse, breakfast, lunch and snorkeling.  A rather good deal.  You can also hire a boat by the hour or day. Prices generally vary on distance traveled.  Gasoline runs about $1.25 a litre.

Boat trip to the islands

Some detailed SihanoukVille Travel Information from Ana Travel