I don't know about the rest of Maryland but in Montgomery, MD you cannot vote early unless you do so by absentee ballot.
If you want to vote by absentee ballot, the deadline to request one is:
Tuesday October 28
If the request is mailed it has to be at the Montgomery County Board of Elections by 4:30 PM
If you fax the request, you have until 11:59 PM
I'm disabled and have no car so they sent me a form to request an absentee ballot. In the envelope the form, a little slip of paper stating the date of the deadline. A fax number or phone number was not included so you'll have to call for that like I will on Monday.
Here is the website for the Montgomery County Board of Elections