Oldie looking to relive my youth

I'm relatively new to this area and i have been out of the saddle for sometime,due to a mixture of illness and lack of fitness.I have recently started to participate in solo, moderate, pleasure rides in the evening and at weekends in and around the local country roads, but feel i need to up my distance and speed, not too mention a change of scenery and some plesant company along route.
I am not always available on Sunday mornings,because of work commitments, but i would like to test my capabilites without committing myself with similar members of the St.Neots cycling community, before i decide to join up.
I would like to think i could manage a group 2 ride and would welcome the opportunity to give it a go.
Do i just turn up in the market square on a Sunday morning,or do i have to register first? Is there a ride planned for this weekend, whereby i could give it a try?