It's a good sign, but not a guarantee, so keep looking.
Since she gave you the menu, study it and be prepared to answer questions about it when she calls. Know all the grilled sub options. If you haven't worked in restaurant - food service before, ask friends who have so you'll be ready if she asks you how you greet customers, how you take orders, how you upsell, etc. (Not sure if this is counter service or table service, so adjust accordingly)
Also know the bus schedule so, if she asks if you could work late/come in early, you can let her know what time and which bus line you can take. Reliability is a top concern for restaurant help. Not having a car may cause concern that you don't have reliable transportation. If you demonstrate that you have thought through how you can work different shifts -- and provide concrete details -- that will likely help your cause.