I train upper and lower together every workout. I split my workouts up either push day or pull day on a 3 day/week cycle. Push day quad based exercises (even deadlifts), chest, triceps, and overhead pressing for shoulders. Pull is hamstrings, lats, biceps, rear and lateral delts. I do calves on either of the days. This gives me a push/pull/push one week, pull/push/pull the next. Every now and then, I do one of each plus a full body for my 3rd. You could do 2 push and 2 pull a week as well with that split.