1. In my experience most groups agree a set of rules, then everybody signs a bit of paper when they join agreeing to abide by them. Make sure you include sanctions for non-observance (i.e., how to throw people out!)
2. Most syndicates have a booking system and a rule that prohibits any member from having more than X number of days booked ahead at any time.
3. Public transport.
Nothing wrong with any of the types you've mentioned, although for that low money you'll probably only get (of the PA28 family) a -140, which isn't the most flexible aeroplane in terms of runway length and payload.
Two other types I'd look at would be a Rallye (but have it checked for mainspar corrosion) or the PA38 Tomahawk which personally I think is a much nicer aeroplane than a C152 and probably cheaper as well - certainly it's no less capable as a training aeroplane. Also don't discount the occasional unusual aeroplane - something like an Auster or Tripacer for example.
G