Sad to say that I saw a truncated version of On the Old Spanish Trail, one that must have been edited for television as a previous reviewer mentioned. And it was black and white.
What little I saw convinced me it was a good film with both lots of music and a good plot if you could fill in the blanks.
There was a sequence missing, but alluded to in the film I saw about Andy Devine believing he dreamed he saw the villains trying to break Tito Guizar out of jail. If so it must have been a very funny sequence as only the befuddled Mr. Devine could make it.
Because we had not only Roy Rogers, but Tito Guizar and pinch hitting for Dale, Jane Frazee there was a lot more singing in this than normal. Great for those who like singing cowboys.
I believe Dale might have been on family leave from Republic. She and Roy had only one natural child from their marriage, they adopted two others, and she and Roy both had kids from their previous marriages. (Yes they were married to others, Roy's wife died and Dale was divorced from her first husband). Jane Frazee though is a fine musical performer and fills Dale's cowgirl outfits out just fine. Roy and Dale's child would have been born around the time this and a succeeding film came out.
Best song of the picture is the title tune. Both Rogers and Gene Autry recorded extensively from their films, though Gene had far better success as a recording artist than Roy did.
If you get to see On the Old Spanish Trail, try to see a full length version.