Cut the ends off of the green beans and slice into pieces about an inch or so long. Fill a medium-sized pot halfway with salted water. Bring to a boil and add the green beans to the pot and boil for 5 minutes, or as long as it takes for the beans to get tender (or tender-crisp if you prefer). Green beans can be highly variable in how long it takes to cook them to tenderness. More mature beans can take up to 20 minutes.
Drain the green beans and rinse with cold water to stop the cooking process. Drain well. Place them in the bowl with the pinto and black beans. Drizzle the olive oil over everything and toss to combine. Mix in the green onions, jalapeno, garlic and cheese.
In a separate bowl, mix the lime juice and sugar until the sugar dissolves. Add the mixture to the salad. Coat the beans well and let marinate for at least 1 hour, preferably several hours. Just before serving, toss in the cilantro and adjust seasonings.