Basically it's we come in peace. Also, thanks to TFWiki, there's hand signals to go with the words long as you have five digits. Edit: apparently in the comics one translation is "Do you hate dirtwad Decepticons as much as we do?"
Stage 1: Raise the left hand, palm outward to the person being addressed. Keep the thumb tucked to the side of the palm, pointing upward. Clench the index and pinky fingers as if making a fist and extend the middle and ring fingers vertically. The gesture should be made at the same time as speaking the "graaaaagnah" part of the verbal Universal Greeting.
Stage 2: Extend the index, ring and pinky fingers. Curl the middle finger and thumb towards the palm of the hand so that they touch at right-angles, with the side of the thumb's tip pressed against the nail of the middle finger. This should be done in time with the verbalization "wheep".
Stage 3: Clench the index, middle and ring fingers. Extend the thumb and pinky fingers so that the gesture resembles a horizontally-flipped 'L'. Shake the hand sideways twice, in time to the syllables of "ni ni"
Stage 4: As the final "bong" is spoken, open your hand out so that all digits are extended and slightly splayed, as if to make a hand-print in clay. Pause momentarily and then press the thus-opened hand against that of the person you are addressing, who themselves should have a likewise open palm.