Sure.

Here is a link that might be useful: Garden Gate

Martha Washington (otherwise called "Regal Geranium)...pelargonium domesticum, will set buds when the cool of the evening is given them.
They may not do well in flower production when given hot summer conditions.
But by all means, do cut them back to relieve their legginess and give them good sunlight.

Legginess is usually caused by not giving the plant sufficient sun. But inside, use caution about putting the plant so close to the window at this time. The sun is still very high yet and through the glass can increase the temperature of the soil dramatically.
Why not put the pot outside and let the plant enjoy what sunlight is still with us. The cool of the evening will help set buds. There is lots of time left before worrying about frost and having to take the plants indoors.

This is late but I have to drop this in here. There is only one reference I have ever seen that gives solid advice about these types of Pelargoniums. Thalassa Crusoe's "Making Things Grow Indoors". She has quite detailed and easy to follow instructions in her book...and was a great, not mention amusing, writer. Pick it up sometime at a used bookstore...you won't be sorry.

Dave
Milwaukee