Go through your results for flights to Ciudad Obregon in Mexico with Netflights. Although Air France usually has the best prices, it's best to double check what's available for your travel dates.
If these flights are too expensive, try searching for a different time of year. It's likely that prices for both flights and accommodation So if your dates are flexible, consider looking at different times of year.
But if you're struggling to find flights to Ciudad Obregon that work for you, try looking at other airports in Mexico.
For even more options, check what other airports you could fly to Ciudad Obregon from. You might be able to make a saving by going from a different airport or city.