I think a better choice for low quiescent current would be a LP2950 voltage regulator.
The LT1086 (similar to the 7805) needs 5-10 mA, the LP2950 less than 100uA for himself.
Are the 70mA constanty drained into the PIC or also the rest of the circuit?
You can put your PIC into sleep mode and reduce the current consumption to a few uA.
If you make your transmitter circuit switchable by the PIC you should be able to reduce the standby current to the 100uA range.
If this is not sufficient, I've seen circuits where the uC switches off its own power supply and is powered up by a key-press.

Regards,
Ingo