As for fearing being from an HBCU will hamper your choices, don't fear. There are several HBCUs that are very well respected -- Spelman, Morehouse, Howard, Hampton, Tuskegee, Xavier in Lousiana, Fisk.
I myself graduated from Spelman in May of last year, and I'm currently getting my Ph.D at Columbia University. There are a lot of Spelman, Morehouse, and other HBCU graduates here (one girl in my program went to NC A&T for undergrad). I also know a lot of HBCU grads in the city who work at top firms -- McKinsey (one of my classmates from college works in Chicago with McKinsey, went to Morehouse); Goldman Sachs, Merrill Lynch, Morgan Stanley. Got some other friends who are currently in med school at Penn and WUSTL. A lot of us went on to some very distinguished careers.
The top firms came recruiting at Spelman and Morehouse, including the ones I listed above, top law schools like Harvard, Yale, Stanford and Duke; we always were having graduate school fairs on campus or very close.
Academically Spelman was more of a challenge for me than Columbia is now
I've talked to another Spelman grad at Columbia who feels the same way. The quality of teaching is very good, and they attempt to challenge you and turn you into a professional. I can't speak for other HBCUs, but other HBCU graduates tend to do very well wherever they go -- and hard work and professionalism are valued at HBCUs (any given day about 20% of the campus is dressed up, lol).
As for adjusting to life in a predominantly white environment -- not gonna lie, it was an adjustment for me, but that's also because I had lived in a predominantly black neighborhood and gone to mostly black schools since middle school. Other students who grew up in predominantly white areas will find less adjustment.
And it's not like you won't interact with people of other races, just like students at women's colleges interact with men. There is life outside of school, and there are summer internships, research programs, jobs, volunteer gigs...