Sorry, herts only just noticed this,
When we first started, many eons ago, we requested babies only. We were told, in no uncertain terms, that babies were like hens teeth and they already had a list of "baby foster carers" so we would only get one if these carers were full.
We agreed then, to take any children in the 0-5 years bracket and this we did for many years. In this time we did foster a few new borns but our placements were mainly older children.
A few years ago I became increasingly tired of taking 2 3 or sometimes 4 older children at a time and not enjoying the process much, my heart is with the babies.
I had a long chat with my link worker and told her I would from now on be only accepting newborns. Her response was the same as above but I stuck to my guns and we've never looked back. We have almost always had a placement, we have 2 at the moment so as for my not getting babies pffft
I would say if you're just starting out it may be difficult to ask for a specific age but it depends how busy they are.
Hope this helps.