Do we have anything in orbit around Venus??? It is closer than Mars...and I am sure some science can be had with an orbiter.
The same floating colony idea goes for Neptune & Uranus as well.
ESA's Venus Express is orbiting the planet, NASA's MESSENGER did two fly-bys en route to Mercury. ESA, NASA, JAXA and Roscosmos are all planning future unmanned missions to Venus. Two of these plans include landers: the American Venus In-Situ Explorer and the Russian Venera-D.
But that's all not even remotely close to floating atmospheric colonies, of course.