For bus companies, take Grassland from Beach Road, its pretty reliable and cheap. If not take the luxury bus from Novetel Hotel (Only problem, the idiots there do not pick up the phone! Lazy bums who just sit here and issue tickets so no phone booking possible, not even possible to check if there are anymore seats availiable)
If you want to stay in the city then you should stay along Jalan Bukit Bintang, there are many budget hotels there. RM 50 and below a night. But dont expect anything more than a bed. Petaling Jaya or PJ is quite a distance from the city. The hotel to stay at in Petaling Jaya is Eastin.
For food, eat at Chinatown, there is a famous claypot rice store there, near where all the tourist type of eateries not unlike our Chinatown. Also try their version of grilled stingray. If not eat at the street running parallel to Jalan Bukit Bintang.
If you want to shop at Chinatown for fake goods, its always better to be able to speak cantonese as that is the lingo there, easier to pass off as local. The rule is always if the item is say 50 dollars on the price tag, you bargain until its around 1/3 of the price. I have never heard of anyone getting hit on the head.... mmmm maybe that guy who got hit was really kwa lan to the shop owner???
Basically at Jalan Bukit Bintang, its also a red light district, you will have men coming up to you asking u if you want girls, most spas and health centres at all hotels are covers for brothels. But however if you are street smart, you will be fine.... just dont act loud and let the whole world know you are Singaporean. Be humble and smile and open your eyes, you will be fine.....
I was posted there for a while 2 years ago and when I went there for the first time in my life. I was left alone as there was no one I knew. I ended up clubbing alone by myself till 6 am in the morning ending up in a joint where people were taking estacy and all.... but I survived.....