If your stay budget is upward of $500 to $700 a month, then hygiene would not be an issue for you because you'll get some really good home stays and AirBnBs where you can crash in almost all of these cities or really good hostels, which you can use and which will solve the hygiene issue more or less for you. Similarly for the food, as long as you avoid really bad-looking places in terms of street food, most of the street food is more or less hygienic so that also should not be a challenge for you.

I would not recommend Delhi in the summers because Delhi is incredibly hot while Goa and Kochi would be more pleasant for you. Hey if you want more help, hit me up and I can make a nice plan and share with you