I agree with Wayfer and Johnnie Walker but obviously starting at A Guarda adds another 30 km so your be walking about 145km. Baiona is a beautiful place, I should know I live there !! Another option is to take a short bus ride (services are frequent from Bus Station) from Vigo to Panxón, Nigrán and walk along the coast following the Green arrows to Vigo then follow the River Lagares upstream then when you reach Celta de Vigo football ground just short of Castrelos Park pick up the Yellow Arrows all the way to Santiago. This is a route which my mate Luis Freixo helped to promote see his Blog
http://www.caminador.es/?page_id=117 which is perfectly feasible and really enjoyable and I've done it from Baiona a few times and got my Compostela. I love the section between Vigo and Redondela as you pass through woodland with amazing views looking across Vigo estuary and back towards Vigo.
Day 1 to Redondela approx. 32 km via Vigo (after 17 km) you can rest in Vigo before carrying on or stay the night there.
Day 2 to Pontevdra approx. 20 km so you have time to enjoy Old Town which is second best in Galicia after Santiago
Day 3 to Caldas de Rei approx. 23 km
Day 4 to Padrón approx 18 km
Day 5 to Santiago de Compostela approx.24 km
Buen camino !