Here are my experiences. The pier was my stop prior to boarding a ferry to Koh Rong Samloem. In my opinion, not the friendliest place on the planet, particularly compared to other parts of Cambodia that I've been to. This is perhaps the result of the flow of tourists through Sihanoukville, and this may be understandable. You will read a lot of discussion about ATMs on the little Islands. As far as I know there is one ATM, only on Koh Rong proper (not Samloem). We opted to take our money out at one of the ATMs on the pier strip prior to boarding the ferry. You should know that the ATMs only give out hundred dollar bills, in a community that will not accept them, something I find unbelievably backwards. You would think by now somebody would have spoken to the banks and asked them to put $20s in the ATMs along the pier. What is clear is that the stores would rather not do any business than make you any change. I watched about $250 in sales lost in the lineup I was in in the Mini Mart because they wouldn't honor hundreds. So unless you're prepared to spend more than 50 or 60 bucks in one of the stores closeby or even the restaurants, you should expect that they will not take your hundred dollar bills. Keep in mind this is before you even get to the islands. One store was willing to take our hundred dollar bills as long as they could charge us $3 for breaking it. None of the shops or the restaurants or the mini-marts will take your hundred dollar bills. Having said all of that, if you're planning on heading to any of the Koh Rong islands, don't even wait to get to the pier strip prior to boarding your ferry to get your money. Get your small bills for the islands before you even get to Sihanoukville. We also ate at Walk Coffee, and found it riddled with roaches. As it's the only place we ate, I can't speak for the other restaurants, although it's perhaps not surprising due to its location on the pier.