Going on Bagpacking trip for the first time from to France, Spain and Protugal from India

how many? when? ages and/or impairments? price criteria?

In the month of may and only my hubby and me will be travelling. Looking for cheapest stay and 18 days trip.

Guide with places to visit and mode of transportation within these
places.

Welcome to the RS forums, banhisikhamukherjee,
This is much, much too broad a question for people to be able to answer. The first thing you need to do is get yourself some guidebooks and spend some time with them; they'll help you decide what attractions in each city will appeal to you. A good guidebook will also provide info on local transport options. Websites like hostelworld or hostelbookers can help you locate and book backpacker-budget beds.

So, do some reading and then come back with more specific questions you may have?

Personally? I think 7 locations/3 countries in 18 days is too many, especially if those 18 days include travel to and from New Delhi.

You just have too many destinations for too short a time. Paris and Barcelona have large numbers of attractions. If you like art, Madrid will take a lot of time as well. If you don't like art, you can skip Madrid and just go to Toledo. Nice is a pleasant, large city with some quite good art museums and markets. Otherwise, it's a base for seeing other places (charming though typically touristy) on the Riviera and up in the nearby hills. To go all the way to that area and spend only perhaps two days there doesn't really make any sense.

I'm puzzled about why you chose Porto but not Lisbon. They're both worth visiting, but I think there's more to see in Lisbon, plus there are the palaces in nearby Sintra. I'd skip the Algarve completely.

Whatever you do, you don't want to travel from Spain to Portugal and back to Spain. Transportation between those two countries is very limited and, except for flying, time-consuming. Don't do it twice.

Use the Deutsche Bahn website to check travel times by rail; you'll may need to use early-spring dates to get an approximation of the schedule for your travel period. Buses usually take quite a bit longer. Use Skyscanner to check for flights; they can be cheap if bought early.

For rail fares you'll need to visit the website of the company running the trains or perhaps trainline.eu, which sells tickets for most if not all of them. The super-low train and airfares you can snap up when tickets initially go on sale are non-refundable and non-changeable, so wait until you're sure of your schedule before buying.

In general, the best mode of transportation between Spain and Portugal is flying. Or just stick to one country, since your plan misses some great destinations in each.

• There is night train service between Madrid-Coimbra-Lisbon and between Barcelona and the Spain/Portugal border at Vigo-Guixar (but the next train connection to Porto leaves you waiting in Vigo for 8 hours).
• Direct bus service runs from either Lisbon or the Algarve to Seville, where you can rejoin Spain's rail system. But then I'd want to spend time in Seville, and would even choose Seville over the Algarve.

Rick's guidebooks, and I assume some of the others, will summarize the connection options between the cities covered in the book. You can also see rail maps online. Buses are operated by several different private operators. www.rome2rio.com is one site that helps you compare transport, but then click through to each transport operator to see actual schedules.