10 days in July. Portugal, Spain??

Contrary to what you might expect from looking at a map, the transportation links between those two countries are not great. And ten days is not a long time. So my suggestion is to stick to just Portugal or just Spain. In that amount of time you can get a more comprehensive look at Portugal; it wouldn't allow you even to scratch the surface in Spain. Alternatively, you could think of the trip as ten days in Catalunya, or Andalucía, or Madrid and the many interesting day-trip destinations around it.

Edited to add: From the weather standpoint, in July I'd probably not want to do Andalucía or Madrid. If you want a less citified experience, you could spend time in north-cental and northwest Spain, between the Basque Country and Galicia.

Before going too far down the planning path, check out Skyscanner to see what cities have good flight links (ideally non-stop) to Prague and/or Switzerland. You can indicate that you want to fly from "Spain" or "Portugal" and see what pops up.

Following on acraven's excellent advice, a great way to find out who flies where is to look at an airport's Wikipedia page.

Portugal has airports in Lisbon (center), Porto (north) and Faro (south).

Switzerland has airports in Zurich, Geneva, Basel, and Bern and Lugano (the last two have very limited service).

Spain has lots of airports. Madrid, Barcelona, and Malaga are the three busiest. Some of the others, like Seville, get international service, while some have little or no service except "feeder flights" from Barcelona or Madrid. If you follow acraven's excellent advice to focus on one or two regions of Spain, look at all the airports in the region. For instance, for Galicia, look at Santiago and A Coruña.

Thank you! I looked at Skyscanner and it is so helpful. It sounds like Spain might be worth a trip on it's own. So thinking Portugal and then we could fly from Lisbon to meet our daughters in Zurich to spend 8 days with them in Switzerland.

We love coastal areas and I would like to spend some time in Cascais but will it be crazy crowded? and where else could we go near there before we fly out of Lisbon. Could we drive anywhere? We have 10 days

Sintra is one of Portugal's top destinations, and it is very near Lisbon. The whole country is small, so you have time to see more than just the Lisbon area if you can drag yourself away. My trips to Portugal were not recent, but Coimbra and Porto (both north of Lisbon) are worthwhile, and public transportation is very good in that corridor. Pick up a guidebook to Portugal and you'll learn of many interesting smaller towns like Evora and Obidos. I think it would be nice to have a rental car for few days to loop through some of those smaller places for which transportation would be more time-consuming without a car. However, if you want a relaxing trip without dealing with a car, you can certainly have that.

It's my impression (not based on current experience) that the worst of the tourist hordes are down on the Algarve, which is very popular with northern Europeans looking for sun and beaches. But any attractive beachy area is going to have tourists in the summer.