In general, I'd probably avoid going there on a Saturday, but we could see the museum from our hotel room at the Sakuragicho Washington Hotel in Yokohama so it was a short walk - and we were still adjusting to Japan time and up at the crack of dawn anyway - so it actually worked out well. We arrived about 45 minutes before the museum opened (highly recommended, especially if you want to make your own Cup Noodles.
The museum is located in a really nice touristy area of Minato Mirai 21. It super easy to get to even if you're not staying in Yokohama - you can take a JR train to Sakuragicho Station and then it's a 15 minute walk (or you could take a bus or a taxi, I suppose - we like walking). The area is super easy to navigate and it's not nearly as overwhelming as Tokyo. There's an amusement park and a shopping center very close by and lots of other shopping areas and places to explore in the immediate area. There is lots of familiar American food in this area too. Check out the museum's web site for hours and entrance fee and all that since I'm sure they vary.
We joined the already growing line and waited to purchase our tickets. We almost never had a problem getting English maps and things - at most places we went, they noticed us before we could even ask and rushed to bring us things in English. Japan is awesome like that. The main floor of the museum is open and modern feeling. There's ticket windows and a gift shop and the stairs up the museum.