I'll be arriving in Madrid early a.m. on June 9th and will be traveling alone until I meet up with my boyfriend on June 14 in BCN. What to do in between? He hasn't been in Spain before thus our schedule is as follow from June 14-June 21st!
June 14th - rest day in BCN.
June 15-16 - BCN
June 17-18 - we are nudist... any recomendations on beaches in Costa Brava? Any suggestions for car rental companies?
June 18 flying at 8 pm to Madrid from BCN.
June 19th - day trip to Toledo
June 20th - Madrid
June 21st - back home.
I have previously considered going South on my first leg of the trip - but it might be a tight schedule... any suggestions on what places to visit between June 10th-14th? Should I rent a car from Madrid into BCN .. which cities/towns are a must? Any help is appreciated.

You arrive in Madrid early a.m. on June 9th and have to be in BCN on the 14th. You might consider spending that first full day, the 9th, in Madrid just to recover from the long flight. Spend that day just walking around and seeing Madrid as much as you can. Go to bed EARLY!

Next morning, the 10th, you could take a daytrip from Madrid to Segovia by bus. Spend the night in Madrid.

The morning of the 11th you could take the fast AVE train from Madrid to Sevilla and spend 2 nights there until the morning of the 13th. Then take the train/bus to Barcelona. Wow. That's a long-haul, though.

You might instead of the immediate above, consider going to Valencia and visiting the coast, the city of Valencia and the villages in the province of Valencia. From there, you have a nice, straight shot up the coast to Barcelona.

I'm not so sure you should try a rental car for any of the above transportation alone, female, if it's your first time in Spain and you don't speak Spanish/Catalán.

Anyone else have suggestions/comments?

Saludos, MadridMan

Thanks! I actually speak fluent Spanish - Peruvian born - so that won't be a problem plus I will be coming from Africa from trekking and will have 2 days rest prior to arriving to Madrid - so not much jetlag to worry about... Thanks.. I haven't consider Valencia - but I'll read more about the destination. Any more thoughts?

To me [even though I love Andalucía] it seems a bit OTT to try to get in the South as well. I should not actually go to Segovia either although it would certainly be a smashing day out. Why not consider something which fits better with moving from Madrid to Barcelona?
I suggest strating with the train to Zaragoza. From there you could easily get up to the Pyrenees and spend time at Torla for the Ordesa national park or in the delightful villages of Hecho and Ansó.
I have not much time to spare here at the moment so, if interested, please mail me on davidcross@frogsmore72.fsnet.co.uk and I will send you some stuff I have written on that area.