Watch the Rhumba Patterns online guitar lesson by Andrew Ford from Blues Bass Survival Guide
Mostly when we talk about rumba style grooves in a blues context we are referring to a latin influenced, New Orleans type groove. The drums will vary but the primary bass motif will be a dotted quarter note then an 8th note tied to a quarter, followed by another quarter note. This rhythm is like the first half of the Bo Diddley groove, it is also the same rhythm as the first bar of the 3-2 clave in Afro Cuban music. Spend some time internalizing those rhythms because they can be very useful in understanding creating bass lines. In example 3 I play a sample bass line that uses this rumba rhythm. After becoming comfortable with it you can transpose it and play a complete 12 bar blues form with this pattern.