As someone that has been around the industry since the 0.1b days of Access and Sql Server 7 and before...(the brain fogs with age sometimes) the question you pose is not an easy one to answer.

While it is true that many small and medium size companies have and are using Access, finding jobs with them may not be the easiest thing to accomplish.

While I have to agree that where the opportunity presents itself, using Access as a front end to a SQL back-end; whether express or enterprise is a pleasure to work with and in, the reality of finding businesses that will pay a living wage for someone with Access skills compared to someone with SQL skills in most areas in the country today is like searching for the proverbial needle in a haystack.

My two cents is to concentrate on SQL and if you are targeting smaller businesses as a generalist, not specifically as a DBA, then get up to speed with .NET and web based access to data.