To back up Jesselt's advice, absolutely DO NOT take Taxi's.

Again, the train system might be quite daunting at first, but stick with it and you will be a pro at it within a day.

Taxi's are unbelievably high priced and will drain your funds in an instant.

Yes and no. Depending on how many people are traveling. If you have 5 adults, and a short distance to travel (let say, between 2-4 stops on yamanote or chuo line), it may make more sense to take a taxi. At least, for me splitting the bill between 5 passenger from Tokyo Dome to Akiba was cheaper than taking the metro and train......

Well, that logic very well applies to anywhere in the world if you have 5 people with you, sure.

But all the same, even if you might be saving a bit, unless you have money to burn, I wouldn't take one at all. Something about weening yourself off the convenience I guess.

That's an adequate amount of money for sure, but I hope you have a credit card in case of emergencies etc.

it is because you get stuff in Yokosuka base, given that you know anyone inside. It makes shopping cheap as hell.

I don't know. If you are going to use transportation at all, that costs lots of money already, a simple phone call costs lots, and so do all meals/souveniers. ONLY meals souveniers can be covered by 700 dollars for 12 days, but you need to consider other accomidations as well

No... I don't know anyone inside Yokosuka.. not anymore anyways..... I did most of my shopping off the street, i am not saying that things will always be cheap, just need to shop around and be careful