Nope, but what you can do is minimize the data pulling by setting viewfields. Now is like you are doing a select * when you only need select id
var caml = "<View><ViewFields><FieldRef Name='Id'/></ViewFields></View><Query>your query here</Query>";
After executing the query you just need to cal get_count() as you already do
If you are familiar with jQuery, I suggest you taking a look a this library, is very easy to use and helps you improve your work with object client model. http://spservices.codeplex.com/