You should do one at a time. In your code, you tried to trigger both left and right, and then read left twise.
Also from what I remember there are just two fast pins on galileo so make sure to connect the two echo pins to that
Here is what i'd try
void pingUltra()
{
//----------do the left
digitalWrite(trigPinLeft, LOW);
delayMicroseconds(2);
digitalWrite(trigPinLeft, HIGH);
delayMicroseconds(10);
digitalWrite(trigPinLeft, LOW);
pstart=micros();
while(digitalRead(echoPinLeft)==HIGH){}
pstop=micros();
iLeft = (pstop-pstart)/29/2; //testing only
//-----------now do the right same as above - change variables as needed
}