Do you have a website? I would post a whole bunch of photos of your crew engaged in 'outdoor play' at your local park or other community venues and how you bring things to the park to 'explore' and so forth cause a photo really is worth a 1000 words ... it is one thing to 'tell' parents that we do something but when they can SEE how that looks and works they are more likely to believe it and come check you out in person!

I have peers who are in condos or apartments without 'fenced yards' and they have no trouble getting clients and most of them are full with waiting lists ~ however they do the above show lots of ways that they make their environment WORK to provide children everything they need just like backyard can!

Plus I will tell ya a secret ~ I have a house with a fenced backyard and we rarely use it for 'physical gross motor play' it is basically more set up like an 'indoor classroom' with sensory stations, dramatic play and so forth cause it is small and not alot of room for climbers and swings and so forth ... the community just has so much more to offer than my lil ole yard can so in the morning we always go to a local park somewhere so A) they can get more varied gross motor options depending on the park we choose and B) they can play and explore with other children which helps when you have one who does not have a peer close in your own group and C) it allows ME to meet up with other adults and get a little grown up social skill development even if we do not have time to 'chat' just being at the park with another human for support if you NEED IT is nice

I would not look at not having a 'backyard' as a deterrent ~ you just need to work at SELLING how you are able to meet the perceived needs having a backyard does in clients