"Star Spangled Girl" was one of many Neil Simon movies in the 70s. It doesn't compete with "The Odd Couple" or even "Seems Like Old Times" which have better scripts and don't seem as dated.
This movie is straight out of the 70s-- very reminiscent of the "Mary Tyler Moore" show or "Love American Style." In fact, it seems more like a made-for-TV movie now than a theatre release.
That said, it's a cute romantic comedy-- Sandy Duncan and Tony Roberts are enjoyable, and it's fun to note the classic 70s dress, storyline (the 2 leading men produce an underground newspaper while Sandy Duncan is a flag-waving Olympic swimmer), and music. Davy Jones (of the Monkees) sings the theme song.
Is it a great movie? No. In fact, some will probably find it annoying. But if you can handle "cute" there are some classic Neil Simon funny lines, it's G-rated so it's safe to watch with kids (although it's probably too talky for them), and it's worth the bargain price if it sounds at all appealing to you.