Here is a list of ideas to save money when visiting the Napa Valley.
There are several low cost options for visiting wineries such as Hopper Creek Winery which has free tasting. You will have to call to make an appointment with them and most wineries. It is worth it! You will learn a lot about wine from visiting them and other small tasting rooms.
Tasting at most Napa Valley wineries is about $10 to $40. Often if you buy wine they will waive the tasting fees. I tend to select small wineries where wine is made for passion over profit. Often at these places you can learn about the process of making wine from the person (winemaker) who actually creates the wine. The other advantage to this is the tasting fees tend to be less expensive.
Also you Can share a tasting. You do not need to buy a separate tasting fee at most places. The only exception I know to this is Castello di Amorosa where part of the fee is to explore the castle.
If you are planning a half day trip I recommend staying in small geographical area so that you can get the most in during a small amount of time. Such as Oak Knoll/Stags Leap, Oakville/Rutherford or Carneros appellations.
If you have time visit Castello Di Amorosa. It is fun as it is modeled after 13th century Tuscan castle. I believe it is $20 for a tasting there. And it has nice views. It also has an excellent gift shop for adults and children alike. No appointment needed. Most of the wineries in that area tend to be more expensive on their tasting though. But you can visit the castle first then work your way back down the valley.
It is less than an hour to get to the Carneros district and about an hour and a half to get Castello di Amorosa from San Francisco.
Lodging is expensive in Napa. One of your best low cost options would be the Best Western though it is still over $100. You can also search hotels and vacation rentals through our lodging page. Vallejo which is in the next county has some low cost hotels however it is not nearly as nice or safe. You can also try Airbnb to find economical lodging.
Since you are aiming to stay on budget I recommend Mexican food such as Villa Corona-in Napa and St Helena..
There is also an excellent deli in St Helena-Giungi Grocery. It gets busy but is worth the wait.
In Yountville- Ranch Market or Pacific Blues Café.
If you are in the Oak Knoll/ Stags Leap area Soda Canyon store has a good deli.
In the city of Napa any Mexican place will do and Small World Cafe in downtown Napa. Local secret spot though would be Uva where plates start at about $12.