It's more complicated than that. A Hoffman transfer represents the minimum energy needed to change from one orbit to another. The closer you are to the body being orbited, the faster your velocity. When you're in a highly eliptical orbit around the Earth, maximum velocity happens at perigee (minimum altitude) and minimum velocity happens at maximum altitude (apogee). Now, the conceptual trick is to realize that in order to go higher, you need to accelerate. However, as you go higher, you're slowing down. Put another way, to speed up (in a lower orbit), you must first slow down and to slow down (in a higher orbit), you must first speed up.

The Earth is traveling around the Sun faster than Mars. To fly a Hoffman transfer between the Earth and Mars, you need to accelerate so that your craft is in a heliocentric orbit with a perihelion at the Earth's distance from the Sun and whose apohelion matches the orbit of Mars. You have to time the transfer so that Mars will be in the right place when your craft gets there, too. Once at Mars, you have to match orbital velocity, entering orbit around the planet instead of around the Sun. This is no mean feat. Even the JPL botched the job in 1999 when their spacecraft arrived at Mars about 40 kilometers too low and burnt up instead of entering orbit.

Now, to return from Mars to the Earth, you must reverse the process. You need to no longer be in orbit around Mars but instead in a heliocentric orbit. You need to slow down so that your perihelion is down at the Earth's orbit. However, as you drop in towards the Sun, you're going to accelerate. You're also going to accelerate due to the Earth's gravitational attraction. The simpliest approach would be to do an Apollo-style direct entry into the atmosphere.

Trying to enter orbit around the Earth would either require burning a lot of propellant to slow down enough or to try some form of aerobraking/aerocapture. Aerobraking involves using the drag from an atmosphere to slow a vehicle, typically lowering its orbit. This has been done successfully at Venus and Mars. Aerocapture involves using the drag to directly enter orbit, perhaps with additional thruster firings or aerobraking to end up in the desired orbit. As Gary has pointed out, they have studied aerocapture but to date, no one has actually tried it.

The matter becomes even more complicated when you consider that a Hoffman Transfer isn't the only alternative, just the most economical one. For a manned mission, you might want to fly faster to shorten flight time. That means you'll probably be arriving at Earth even faster than with a Hoffman Transfer unless you have sufficient energy to slow down as you get closer. Suppose you had a long duration engine like nuclear propulsion that allowed you to accelerate to a very high velocity. You could either keep that extra velocity as you approach the target and deal with it there or you could turn around and apply retro thrust to slow down. Tricky stuff.