I searched quite some time for everything regarding the MPU6050, but there is just rumors and jokes about the dmp funcionality. One project encorporates the hard reverse-engeneering some wise people did, which is: http://www.i2cdevlib.com/docs/html/class_m_p_u6050.html
This also uses the interrupt, which I suppose you can't really avoid. Why exaclty this would be necessary though, is not a thing I could tell you.. I assume, that the dmp works somehow with the fifo buffer and can only interact through it. The cited library has examples with and without dmp, which I can really recommend.
Using this thing for a quadcopter however I can just say, that the dmp is too slow to control such a fast system, so maybe first consider what you really need. From my experience it does some magic things, but acts strange is due to it's not documentary it is a pain to work with.
Hope this helps.