The ANSWER Coalition has:
…secured another permitted assembly area for an even larger gathering site on the parade route, the Navy Memorial (8th St. and Pennsylvania Ave. NW).
See: ANSWER Coalition for details and ways to support.
If your not interested in “permitted” protesting, it could be the case that attendees and protesters alike find it difficult if not impossible to attend the inauguration. See protests for an ongoing series of speculations in that direction.
PS: I remember the Constitution reading:
Congress shall make no law … abridging…the right of the people peaceably to assemble…
NOT:
Congress shall make no law … abridging…the right of the people to be permitted to assemble…
Do you?