In a large, heavy pot over low heat, warm the olive oil. Add the jalapeño and garlic, cover and cook, stirring once or twice, for 3 minutes.
Add the tomatoes and green onion, raise the heat slightly and cook uncovered, stirring occasionally for 3 minutes. Add the beer and clams.
Cover the pan and raise the heat. Cook the clams, stirring them occasionally, and transfer them with a slotted spoon as they open to shallow serving bowls. (The time will vary, from only a few minutes to as long as 20).
Discard any clams that have not opened after 20 minutes. Pour the broth through a fine mesh strainer set over a deep bowl or measuring cup. Spoon the tomato mixture from the strainer over the clams, dividing it equally.
Let the broth settle briefly, then spoon it over the clams, leaving the sandy residue behind.
Sprinkle the cilantro over the clams and serve immediately, accompanied by lime wedges for squeezing, if desired