You need to 'get the word out' in the community as quickly as possible. See what you can do about getting the sign put up ASAP. You might consider a quick - disposable sign - or having the window painted, if you can't get the sign for awhile.
If there is a local paper, send them a 'press release' with the dojo opening notice, along with a short blurb about Aikido and your backround.
Distribute your flyers to the surrounding area - see if other merchants you support will post them for you. See if local apartment complexes will give them to residents, post in supermarkets. Go to the local police department and offer to teach them for a reduced rate. Post information at local community colleges.
Don't worry about small class size. It is really better for beginning students, they get a lot of individual attention - private lessons, for awhile anyway.
Be patient, it takes time.