How can I discourage mud dauber from nesting at my entrance?
They build their nests in the late-summer to fall and I've found the best approach is to remove the nests as they build them.  You'll hear the characteristic high-pitched buzzing as they deposit the mud.  Scrape the nest off the wall or spray it off with your hose.

Mud daubers are not very aggressive, they can sting but usually don't and they don't swarm like hornets do.  Their nests make a real mess, however.  I have never noticed them reusing the same nest although they may build more mud tubes adjacent to old ones.

They tend to like shady spots like you have there on your porch.  The nest is filled with spiders that are paralyzed by the venom and are used to feed the youngsters when they hatch.