Content is king. The words you use, especially on your home page, can make all the difference in terms of your placement in search engine results pages.
As you are writing your home page content and introducing your restaurant to potential customers, try to think of one or two sets of keywords you want to target for searches. These keywords should be fairly specific. Targeting for a keyword like "pizza" or "tacos" will do you no good unless you are a national chain like Pizza Hut or Chipotle. Just imagine how many restaurants are competing for those keywords! However, optimizing for "vegetarian pizza in seattle" or "vancouver fish tacos" can be a realistic goal.
Once you have picked these keyword sets, sprinkle them throughout your page content, always in the same order.
If you are optimizing for "vegetarian hot dogs in portland", you might want to have a sentence somewhere like "Looking for great vegetarian hot dogs in Portland? Come to Alfonso's!". Try to avoid changing the order or pluralization of the words (like "Vegetarians in Portland love our hot dogs"), but definitely keep it sounding human.
Don't stuff keywords into the page.
One to three instances per page should be enough. Any more can get you in trouble, and even cause a drop in ranking. If it looks forced, you should try different keywords or think of a better way to incorporate them in. The idea here is to write what you would have written anyway, but with your keywords consistently appearing in the same order, wording and pluralization. Don't interchange subs, sandwich, hoagies, and po' boy throughout your content!