Depends on what type of coffee. Typically espresso uses darker roasted blends which actually have less caffeine. FOr example and Italian roast has less caffeine than french roast. It also depends on how strong the coffee is. Here is some more interesting info which will guide you against latte's<br />
http://www.cockeyed.com/inside/coffee/coffee.html<br />
And finally, if you order some complex bullshit like a double-tall, half-caff, skim Mochachino with light foam & two ice-cubes, you are 50% more likely to have someone spit in your drink.