That sounds a lot like the "B" group I ride with. Twice a week we go out from the local shop and they split into 5 groups: one "A," three "Bs" and a "C." The B groups are, from fastest to slowest, Killer Bs, Honey Bs and Bumble Bs. I ride with the slowest B group and routinely finish midpack with an average of 18-18.5. That means, after factoring our traffic stops, most of the cruising is done anywhere from 19.5 to 22 or so, with occasional faster stretches depending on mood, gas and wind.