It is hard to give advice. You say you have 1 week to walk. Have you planned your arrival in Spain, and do you have time allocated for arrival, travel to another start point, and overcoming jet lag? It seems to me that the transportation logistics could be a major factor in determining what section you would choose to walk.
With those constraints, I would probably choose to walk somewhere close to either my arrival city or my departure city (Barcelona) but I have experience walking in Spain and my Spanish is quite functional. If you want a "taste of the Camino" I would suggest one of the more popular routes.
For one week, perhaps the Santiago to Finisterre and/or Muxia would be a better choice. You would enjoy good infrastructure, meet other pilgrims, see Santiago, and have good transportation connections to/from Santiago. However, remember that Santiago is a long way from Barcelona (and Madrid) so you need to allow time and budget for that!