Not necessarily. The dedicated new member rides are once a month. If you have never ridden in a group before you should wait for one of these.
If you are confident in a group, for example, you have experience with another club, you are welcome to do join the clubrun on other Saturdays: email Brian as above. Please note, if you are dropped from a clubrun, the group may not wait for you, so if you are unsure whether you can hold the pace, the new member rides are a much more suitable starting point, as no one gets left behind.