If you want to check that if SQL server is available then use
SqlDataSourceEnumerator[
^] as Mika said and if you want to see if they are express version or not try to run this query on them :
select @@VERSION
If there was and
Express Edition
in output string then it should be an express edition.
But also consider using an install program for your program from third parties because they handle all prerequisites for your program and you will not worry for this issues any more.