A great time for impeach Obama protests on an overpass or a street corner would be in the days before Obama State of the Union address, which will be on January 28th, 2014. The state of the union frankly sucks right now and in large part due to Obama.
Publicize your protest by uploading photos/video to the Internet and notify you local media 1-2 days ahead of the protest. All publicity is good publicity. These impeach-Obama overpass protests really took off due to negative publicity about the so-called 10-mile traffic snarl attributed last summer to a protest in Carlsbad.