Lots of clubs around doing organised racing, but if you wanna do your own thing - just do it!
Get a few RC mates together, play your cars at a convenient place and before long you'll have other curious ppl coming up to ask you questions etc etc!
Heck, even if you cruise the suburbs at night you'll soon find nightowls out there with their RC. Usually at the train station or supermarket carparks where there's lighted paved areas.
If you're organising your own - go for it. Put a sign up at your milk bar or nearby schools, you'll be surprised how many RCs are out there. Especially at this time of the year, right after Xmas.
However its always good practice to try ask persmission of the owner of the land/area your trespassing on.. and don't make a nuisance of yourself. If any of you be an idiot and leave a mess, you sure won't be welcome back AND YOU'LL GIVE A BAD NAME TO ALL RC'ers, OK?
If you haven't realised, your freq can be changed by putting in different CRYSTALS. Xtals come in pairs, one in the TX and the other in the RX. They're the little 2-legged plug-in chips (Futaba has plastic handles on them) with the freq printed on it.
You can change xtals amongs the same 'band'... ie 29.xxxMhz to another freq in the 29.xxxMhz band. However on simple AM radios you cannot change to another band eg 27.xxx or 40.xxx without changing thewhole radio.
AM xtals aren't very expensive, maybe around $20 at LHS. If/when you go racing, they normally expect each one to carry sya 3 different sets so you can solve freq clashes when they happen.
In Australia we can use 27Mhz, 29Mhz & 40Mhz for cars. 27 & 29 are the common ones, 40 is quite rare with the basic AM radios.
With 27Mhz, you've got 6 main channels & 6 "splits" (the .5s). Try and stick to the mains, the splits may cause interference sometimes.
ps: IGNORE the "Receiver" freqs listed above. Whenyou say your freq, only pay attention to the TX one - that's all it matters. Do not get TX & RX mixed up either, they should not be installed wrong way round.