Does not help you get accepted unless you really connect w a particular professor that you want to work with. But it might help you make up your mind, which is the way you should be living your life anyway.

Does anyone with experience attending open houses for march II programs know if there is any value in bringing a printed portfolio? 

Doubtful. They aren't actually recording any information, so how could they really remember you? As gruen said, unless you connect effectively enough with one of the faculty so as to start a communicative relationship (email), you won't getting any 'bonus points' for showing up. They are information sessions.

While I totally agree that there are no brownie points for attending an open house, I do think they are helpful in learning more about what kind of place each school is, and therefore what they may be looking for in their applicants. It can also be helpful to chat with other prospectives and current students. Bringing a portfolio (especially a printed one) can be useful if you're ballsy enough to whip it out and ask people for advice. Just be humble when showing your portfolio--remember you are asking for advice, not showing it off!

So I'd still go to at least a few open houses unless it'll completely ruin you financially.

Much of what you ask can vary greatly from school to school.  You should visit to the extent possible, but you could always do so after admission.

If you go before, I would absolutely bring your portfolio and ask for insight.  Remember, you can always visit by contacting a school - not an Open House day.

If you cannot attend, ask to connect with a student via email or phone.

Visiting a campus is more than an information session; it is a chance for you to learn if a school is best for you.