The most helpful thing in this post is the above map, which shows the route for tomorrow's El Comite March for Immigrant and Workers Rights. It begins at St. Mary’s Church (20th Avenue and South Weller Street) at 3 p.m. and will end with a rally at Westlake Park downtown.
As Ansel reports in this week's Stranger, there are other marches and rallies planned for tomorrow. The SPD describes that situation this way:
There is also the possibility several other un-permitted demonstrations may be held in the evening at Seattle Central Community College and Youth Service Center at 12th and Alder. As the organizers of these events have not filed for permits, there is no official route map for these rallies.