just came back from sg. lembing. below are some of the accommodation details we found
If you come by bus (no private transportation), it is best if you stay in Sg. Lembing town. We found only one guesthouse right in the middle of the town. We saw many young ppl near the lobby, and it gives us the feel of a backpacker lodge.
Sg. Lembing Rest House
019-9082193
019-9040389
019-9161492
012-9009622
If you come by bus but wish for a quieter accommodation more suitable for family, you can try this but it's about a km (i think less than a km) from the town.
Hotel Sungei Lembing & Cafe
019-9981126
09-5411924
We stayed here during our trip. Nice, clean and budget. We stayed in a double bed room with a/c and bathroom for RM50 per night, and a 4-person room (one double bed and two single beds) with a/c but shared bathroom for RM60. This hotel is actually more like homestay with regfrigerator, television, clean drinking water, bathrooms (three shared bathrooms downstair and one upstair), shower cream in each bathroom (but we couldn't find shampoo) and towel. It is located less than a km from the town market, near the police station. Its location is at the crossroad to Rainbow Waterfall, Gunung Tapis, Hot Spring, Deer Farm, Orang Asli Settlement. The owner operated a restaurant called Yong Seong Restaurant 永顺茶室 that serves vegetarian dishes. Its 'wat tan hor' and ketchup noodle are featured in chinese magazine called Travelmate 旅游玩家 2007 Oct/Nov edition (i bought this magazine from the restaurant itself).
The two accommodation above are located on Jln. Sg. Lembing, which means you don't have to cross the river. The other accommodations we found are located on the other side of the river, which i think you will need a private vehicle to travel to (the bus only stops along Jln. Sg. Lembing) unless you are a serious walker/trekker.

Lembing Village Resort
09-5411831
019-9070854.
Sg. Lembing Homestay
09-5412395
Operated by the manufacturer of Sg. Lembing noodle (I dunno if there's more than one manufacturer, but this one is across the jambatan gantung). We got to know this when we bought some noodles from them. Its a small double storey brick house with three rooms, costing RM200 per night for the whole house).
ACF Retreat Centre
019-9551405
There's also a nice bungalow with garden called Lembing Resort, but its signboard does not list any phone no. We saw a few singaporean car parked at the front. If anyone has stayed here before, please provide its contact details here.