This year, now that I'm in the US, NOBODY is coming to the US for spring camp. Go figure.
The official Big 6 site some of the spring information up:
Camp Regional Preseason
Rikkio: 3/8 - 3/19: Saito City, Miyazaki 3/1 - 3/8: Tokai Region
Waseda: 2/28 - 3/2: Urasoe City, Okinawa
Keio: 2/28 - 3/15: Ishigaki City, Okinawa 3/15 - 3/21: Tokai Region
Meiji: 2/16 - 2/24: Numazu City, Shizuoka 2/27 - 3/10: Kyushu, Kansai, Tokai
Hosei: 2/20 - 3/2: Kamogawa City, Chiba 3/2 - 3/4: Kisarazu (Chiba)
Tokyo: 3/9 - 3/20: Miyazaki City, Miyazaki
(The Tokai region is kind of the part of Japan between Osaka and Tokyo, so like, Nagoya and Shizuoka and such.)
And here's the entire Big 6 preseason game schedule, in Japanese. All the games are either at the colleges' home fields or at the opponents' home fields, with the exception of the 3-day industrial league exhibition at Jingu, which appears to be from March 31 (thurs) to April 2nd (sat).
I'm guessing that Opening Weekend is still April 10/11, since only Meiji and Hosei still have preseason games going on until then; they were 3rd and 4th place last fall so they don't have league games until the 2nd week of the season anyway (the opening matchups will be Todai-Waseda and Rikkio-Keio). I still doubt I'll be able to stay in Japan that long during my March trip.
Patrick pointed out that the biannual USA-Japan collegiate match is going to be in North Carolina over July 4, apparently, so I'll hopefully be able to go to a game or two of that, and I'm pretty sure a few of the Big 6 boys will make the national squad (like Meiji's Nomura and Keio's Itoh and hopefully Hosei's Taki), so I'll get to stalk them there.
And speaking of Big 6 players that I used to stalk, here's a funny article about the Baystars ni-gun squad showing up in Okinawa, for their spring camp. Kisho Kagami's mom is from there (from the Tomigusuku area, it seems) and has a bunch of sisters and a whole bunch of her family still live there, so about 11 of his family members showed up at the Naha airport to greet him with signs and t-shirts and all. The Baystars will play against the Carp in July in Naha, so his family hopes he'll be at ichi-gun then and plans to have a big family cheering section for him, an "itoko-kai" (or "Cousin Clan" basically).
As for Kagami, he said, "It was REALLY embarrassing," and laughed, "but I'm glad that my grandparents and family members were so happy. I'll have to do my best because they came to support me [and so they can in the future]."