...caffeine than regular coffee.. is this true? I always thought that expresso-being that it's so strong and bitter -is loaded with caffeine.

There is a good deal of confusion about whether an espresso contains more or less caffeine than other typical servings of coffee. The confusion is understandable. On a per-volume basis, espresso contains approximately three times the caffeine content as regular brewed coffee (50 mg per fluid ounce of espresso versus 14-22 mg per ounce for coffee). But measured on a per-serving basis, a strict, one-fluid ounce shot of espresso (with 50 mg of caffeine) has about half the caffeine of a standard six-fluid ounce cup of American-style coffee, which varies from 80 to 130 mg.

this is true.
Just because espresso taste stronger it actually has less caffeine. I believe this is because the water to make espresso is pushed thru faster and and a higher pressure so it has less time to absorb the caffeine. Where as regular coffee is dripped thru @ a slower pace. Hence picking up more of the caffeine

the manager is essentially correct...sort of. what he is referring to is what is considered a single serving of each beverage. a single shot of espresso is about 1 oz of liquid whereas a small coffee is about 10 oz of liquid. comparing them like this the shot of espresso does have less caffiene than the coffee. if you compare them oz to oz then obviously the espresso is more concentrated and therefore would have more caffiene. I hope that clears things up for you.