On the north side of Pasadena, mostly Latino residents live amid broken sidewalks, faulty drainage and pockmarked streets. On the south side of Spencer Highway, where most residents are white, municipal parks are manicured and the streets and sidewalks are better maintained. The disparity in infrastructure is at the heart of a voting rights case that opened in federal court Thursday in which a group of Latino residents is challenging the city’s newly revised system of government, saying it discriminates against minority voters and intentionally dilutes their power. By creating two at-large council seats and eliminating two of the eight district seats, the suit says, the city violated the federal Voting Rights Act, making it harder for Latino-backed candidates to get elected and leading to unfair allocation of resources.