The protest planned by ‘Pro-immigration activists’ for May 1st may well make their point in the southwest and New York, as said activists plan to “close down” these cities, but I do not believe that this is going to help their cause. I rather suspect that such a massive protest will cause enough media attention and economic disruption that the response may be overwhelmingly negative. I do not believe that most Americans have a problem with illegal immigrants qua individuals, but with their apparent disregard for American law and custom (re entering the country illegally). With a group of people of this sort flexing their social/political muscles, I think that a large number of people will feel somewhat threatened by them.
Whether or not this view of illegal immigrants is justified, this protest (amounting to a small-scale economic attack on several cities) is likely to raise hackles across the country, and not just among those who already oppose illegal immigration. America tends to get fairly upset about economic interference, so going for a perceived weak spot like this is likely to stir up more trouble than the protesters imagine.