Demographics are generally the biggest indicator of the crime rate in urban areas, and Vallejo is home to many unemployed people. The City has always been poorly run, and part of their 'plan' for generating income has been to jump on HUD money and invite builders to construct large low income apartment complexes, which over time become ghettos. Other factors are the number of police, post Bankruptcy, I think Vallejo is down to about 90 cops. Since Mare Island was closed, there are really no large employers in Vallejo, so people who live there either don't work, or if they do work, it's probably in the bay area which means a commute involving either one or two $5 bridge tolls (or a ferry ride to SF). As far as proximity to Oakland, it's probably best if you go to Google maps and plot the distance between Vallejo and the part of Oakland you are interested in.