Singer-songwriter Leon Russell is walking a legal tightrope this week.  The Elton John collaborator is expected in a Los Angeles courthouse today to respond to a lawsuit filed against him by his ex-wife Mary Bridges.  Russell was scheduled to trek from New York by road following his appearance with Elton on "Saturday Night Live" over the weekend.  Last week a judge said that Leon's refusal to fly wasn't grounds to push his entire trial back to May, as his lawyers had requested.  Bridges is suing Russell over earnings she claims she's due from his works.