Why should I have to engage someone to go with someone?

As a sign of real respect,  you would feel disrespected if a person who can not speak your language was to arrive at your door unprepared and expect you to make time in your day to assist them, If they did not do even bother to ask someone to translate for them or ask you first if they can come that day.

As well I believe you will get way more out of the experience if you can communicate with the monk and have any questions answered. Sadly many  younger Thai people have little of no knowledge of the Sak Yant or the terms that are used when talking about the subject. So better take someone who is versed in the Thai and English vocabulary of this subject who can better assist .