Private or public foster care

My husband and I have our hearts set on adopting from foster care. I have been visiting adoptuskids.com for years and I can finally see this becoming a reality. We are trying to figure out whether to go through public or private foster care in Maryland. We are moving to a two bedroom home next month, so we will only have one bedroom to share. Our goal is to focus on adoption from foster care for an older child. After we move to a larger home in the future, we then would like to be able to foster and, Lord willing, be able to adopt again. We don't have any children, so we are eager to grow our family soon. My question is this: if we get licensed through the public foster care agency, would we be able to inquire about children on adoptuskids without having to take many children who are not up for adoption? Or is it best for us to use a private agency if our goal is to foster to adopt? Thank you for any information you can provide.