No, at least not to march, not even to deliver a letter to the government, not to do anything official, anything even kitsch, as putting flowers at the Bolivar Square as Venezuelans used to do. The only way some oppo can even get close to the place and not be attacked is if he dresses up as a tourist and goes alone. If they do try to go there or perhaps even if they don't, but are just too close, they get tear-gas and bullets from the police...the same police I said before are 150 times more likely to be criminals than the average Venezuelan.
Blogger Miguel, who was there, reported it all here.
And if the opposition does not like it, they get the most obnoxious speech you can imagine from someone who is supposed to be a police agent (here if you speak Spanish).