If you're interested, and you have a chart, by all means work out a route. After all, you can't do any flying on the ground. Learning anything about flying will be useful, even if you don't have all the required knowledge and get it wrong. Just getting used to the chart terminology and what everything means will be useful.
As an instructor, I'd be quite happy if a new student did that, unless he made a big deal about it... sort of, "look at me, aren't I wonderful, I worked out a route". I can't see your instructor being upset about that; if he/she is, then change instructor!