The graduation rates and grade point averages of women engineers at many engineering schools are as high as or higher than their male counterparts, and most universities track those statistics. Direct questions to admissions departments at the schools of interest asking for those numbers should yield an answer. In addition, web sites are an excellent source for learning about the philosophy of each Engineering School, and the programs they have available for students both inside and outside the classroom.
But the best thing to do is visit some universities and speak to the students to get a sense of the environment and whether their programs are a good fit for you. The amazing opportunities available across the country will quickly become apparent.
You may also be interested in enrollment and graduation statistics provided in an annual report published by the American Society of Engineering Education called By the Numbers. See the most recent 2008 report at http://www.asee.org/publications/profiles/upload/2008ProfileEng.pdf.
Two resources that support Women in Engineering are:
The Society of Women Engineers (SWE)(if the campus does not have a chapter, that would be telling)
Women in Engineering Proactive Network (WEPAN)(They have a Knowledge Center at http://wepanknowledgecenter.org/web/guest/home.)