BUEN CAMINO that is what every pilgrim wishes every other pilgrim when we meet on the trail or passing a pilgrim resting somewhere. It sounds like 'BON CAMINO' and is usually the second greeting after 'Ola!'. Hola is used to greet any person, pilgrim or not, and is primarily used in the afternoon because morning greetings are usually Buenos Dias (good day) which is often shortened to Dias or even Das. Even if you know little or no Spanish, as I do, these words you'll learn pretty quickly just walking the camino.
Other than that it depends on how much you want to learn or how much you rely on the Spaniards to speak English. I found in 1999 that people under 25-30 would usually speak some English because they apparently learn it in school.
Today that age group has grown to 40-45 and it makes communicating a little easier. In the beginning of the hike you can figure out some of the words on a menu, later on, after having seen some English language menus you even start to recognize the Spanish words for certain dishes. Although a few times I have been surprised with what they put in front of me. Not to worry, usually you are hungry enough to be brave and try it and most of the time it is a pleasant surprise.
The town I am in right now, Sarria, is the starting point of the camino for about 25% of the people who walk it. It shows because the town at times looks like it is overrun by people who seem unprepared for the 100 km hike. They either have huge packs, or no packs and use a taxi or 'porter' service to have their luggage moved to the next place. I met a few of them and in some cases I wonder if they will make it beyond the second stage, however I hope I am wrong because some are spending a lot of money to get here and to stay in expensive hotels along the way. Four elderly people from Australia admitted that they rarely had walked more than 15 km a day and never for a whole week every day. You just hope that they don't get themselves into trouble. A friend with whom I walked at the start of the camino for a few days, arrives in Santiago today or tomorrow and reported that after Sarria de trail got a whole lot busier and she was seeing a lot of white legs walking ahead and behind her. Anyway, I'll find out for myself in a few days. Tuesday we hope to start tackling the last 110 km.