spain/portugal planning help needed

When do you start? Early-mid-late September? I would go to the islands first, then return to the mainland.
How do you intend to travel--car for portion or public transport only?
Are you flying home from Portugal?

3 is muddled--both of those are day trips from Madrid.

You don't want to set up an itinerary that has you crossing the Spanish/Portuguese border more than once unless you plan to rent a car for a period covering all the border crossings. The extra charge for a car picked up in Spain and dropped in Portugal (or vice versa) would be very unpleasant--almost certainly at least many hundreds of euros.

There's little public transportation over that border, so combining Spain and Portugal on one trip usually turns out to be more complex than the traveler anticipated. One place where it's relatively possible seems to be in the south. There are buses between Seville and Faro. If you want to cross in the north, it's a matter of heading from Porto to Vigo (not a very interesting city) and perhaps on to Santiago de Compostela and other nice places in Galicia.

Does the order of the areas make sense?
If we have a car we can plan to drop it off before crossing the border to Portugal and then get one again if needed.

I have not searched the transport connections between each place, have you?
You do have a general loop that appears it would work well, but it may depend on where you are flying home from. Again, I would go to the islands first because that is where you might find seasonal change the most impactful.

I'd use skyscanner.com to see which Spanish airports have service to Palma and buy tickets from one city and back to another if possible. That would eliminate one ground transportation leg. The last time I looked there were also ferries; I believe they operate from Barcelona and Valencia, but I haven't checked.

Palma is a city on the island of Mallorca, which has more varied sightseeing options than Menorca and Ibiza. Ibiza is apparently a big-time party island. I haven't been to any of those islands, but the one I plan to visit is Mallorca.

Marbella is not an island; it's a coastal resort in the south, not terribly far from Malaga.

As already mentioned, Toledo and Segovia are near Madrid, not Valencia. They don't fit well with a coast-hugging itinerary.

This itinerary appears to be what you want, but it's going to have you skipping over a lot of Spain's most important historic cities (Toledo, Segovia, Seville, Cordoba, Granada) as well as the capital of Madrid. It would be way too much beach/coastline for me, but if that's your preference, you should stick to it. There's no sense in taking someone else's trip.

Yes. I agree that it's too much beach and not enough city/sites. Suggestions of where to place the ones you mentioned into my existing list?

Also, we have the opportunity to begin the journey in August if that helps with weather conditions.

Inland Andalucia (Seville, Cordoba, Granada, Ronda, white villages) will be miserably hot in August. I'd try to go there in October, myself.

You can check rail routings on renfe.com (the cheapest place to buy Renfe tickets, though sometimes a bit challenging) or thetrainline.com, which will also include some trains run by other providers. I'm not sure The Trainline lists all the trains, though, and there's a small fee involved in buying from that website.

Do not start this itinerary in August! It will be extremely hot. September/October is a much better time frame. How much time do you have for this trip? I hope a lot. 5 to 6 weeks minimum, I would think for an enjoyable trip.

I don't see Granada in your itinerary. I would definitely spend a few nights in Granada. The Alhambra is amazing! And I would spend 2 or 3 nights in Cordoba. There is more to Cordoba than just the Mezquita.

Yes, Granada will be added and we will definitely not begin until September. We are thinking that Madrid needs some attention as well. Where in this order would they (Granada and Madrid) fit best?

I would put Granada after Malaga and before Seville. The ALSA bus from Malaga to Granada is a 1.5 hour bus ride. The buses are modern, clean, comfortable, and air conditioned.

I think Madrid makes the most sense after Costa Brava.