None of these posts are likely to be of much help to the OP.
Balaverde, you don't say what kind of bicycle you want to buy, what kind of riding you want to do.
Many of the groups you see riding the riverside bikeway are sportive riders, if this what you are interested in then most bicycle shops will have organised rides, just search the web for your local shops. They'll most likely have used bikes you can buy too. Another good source of bikes is the Gumtree site on the web. At the budget end there is a bike recycling centre at Montague Road West End.
You can find a list of cycling clubs here.
Cycling Queensland Clubs.
There also quite a few cycle coaching establishments which hold regular rides, MB Cycles and Cam's Cycle Coaching come to mind. And there are informal groups such as the Southbank bunch and the Park Road bunch riding from La Dolce Vita in Milton - just turn up at around 5:30-6:00am most days and jump on the bunch.
For more social rides, If you are a Facebook user, join the Friendly Brisbane Cyclist group, or on Meetup, Brisbane Minglers Cycling Group is more sportive, Brisbane Bicycling Meetup is more social. And if you like touring, the
Brisbane Bicycle Touring Association hold regular local rides and tours.
Bicycle Queensland also run regular events.
No big mountains here but Mt Coot-Tha is right near the city and is a popular training ride. At little further out are Mt Nebo and Mt Glorious, also popular training routes, further out again is Mt Mee. All will give your legs a good workout. There are also many good climbs in the Gold Coast hinterland - Springbrook, Beechmont, Binna Burra, O'Reilly's are all good leg testers.
And finally, I have a 56cm Campagnolo equipped carbon Kuota Kredo road bike I will part with a reasonable price if that would suit you.
