Hi Brenda,
I suggest using www.rome2rio.com for finding transportation connections anywhere. Flights vary by day and time of year, so it will depend on when you are travleling. Looking at a random day in early December, there doesn't appear to be any direct flights from Cardiff to Madrid. You will need to switch planes somewhere, such as Dublin or Amsterdam. You could take the train to London (about 2 hours, 2 trains per hour), which has quite a few budget carriers flying to Madrid - RyanAir out Stansted or EasyJet, Norwegian and Air Europa out of Gatwick. See www.skyscanner.com for flight options. From Madrid, you can fly to Murcia airport (a short drive or taxi ride to Los Alcázares) or take the train (about 4 hours, tickets under 30 euros). See www.renfe.com for Spanish train schedules and ticket prices. To get to Orlando from Los Alcázares, you could fly from Murcia to London Gatwick, which has a direct flight to Orlando.
EasyJet has flights from Bristol directly to Murcia (trains from Cardif every half-hour, taking about an hour). These flights don't go everyday, so again, it will depend on when you are flying. If your schedule is flexbile and you could visit Madrid after Los Alcázares, this might be a good option and easier than going back to London. Then you could fly from Madrid to Gatwick or a U.S. city to catch a connecting fligtht to Orlando. Hope that helps!