I had a long weekend in Cambodia recently and after a day in Phnom Penh, I was taken to Sihanoukville. We went by bus (Mehkong Express) which was actually pretty good. Cambodians pay $5 and Barangs pay $6, which wasn't so bad. It takes about 3.5 to 4 hours to get there.
After we arrived we jumped into a tuk-tuk and headed over the hill to Victory Beach. Most backpackers seem to stay near Ochheuteal Beach, as there are lots of bars on and near the beach and a number of grotty guest houses.
We stayed in the Holiday Palace Casino Hotel. This place is mainly geared up for Korean & Chinese tourists, but the people I was with weren't into mingling with the great unwashed, so it was a much better choice for us.
Checking out prices on the internet show this place to be $28 a night. We just turned up and got our rooms at $20 a night, which was pretty good value. The bed was comfortable and the AC worked well, as did the cable TV.
Also good was the shower, but the bathroom floor was always very wet, so one had to be careful when exiting the shower.
Not a bad view either.