My RV has a 50 amp service. Is their a converter available that will allow me to plug into a 30 amp service and still use two air conditioners? Are they reliable? Who makes them and what do they cost?

Let me Google that for you. (http://lmgtfy.com/?q=30+to+50+rv+adapter)

You need to know the ratings of the A/C's to know if a 30A-120v supply will be enough.

Think about it. You are going(adapting) from a 120/240v-50A supply, to a 30A-120v supply.
The former is a potential 12,000 watts worth of power. The latter is a potential 3,600 watts worth of power. Do you think there is a difference? ;)