I would recommend starting out using some form of Basic. It is relatively easy to learn compared to your other options and allows you to create some pretty nice programs. You can do a lot of things in Basic. Basic has been around for quite some time and you should have no problem finding people to help you.
After you have become familiar with programming PICs in Basic, I would recommend that you grab a book or two (and surf the web for sites pertaining to) Assembly for PIC microcontrollers. This is the native language of the microcontroller and you will find that you will be able to communicate much better with them in the long run if you learn it. Is it difficult to learn? Eh. More so than Basic or C, but only because it's a foreign language and it takes that you think differently about at what you are looking. Basic and C were created to be generally human readable. You might also have an easier time with Assembly once you've had some programming in Basic beneath your belt.
After you've been programming in Basic for a while and learning Assembly as you go, I would recommend moving to C and using either C or Assembly (or both) for nearly everything that you do. C is a much more robust language than Basic and as such, it'll allow you to "tweak" things more than you can with Basic. Consequentially there is also more to learn when it comes to C, but you'll already have the programming fundamentals down by having done Basic and Assembly for a while. C is also very popular for programming anything from PIC microcontrollers up through CPUs and you should find no shortage of information. C is, basically, the "industry standard" when it comes to programming microcontrollers and processors.
Now... Having said that. I'm a Pascal guy. But that's because I've been using it since it's creation back in the DOS days and I have a longstanding relationship with Borland Inprise (who've spent many years developing and distributing Pascal and, later, ObjectPascal). Pascal has never been as popular as either Basic or C, especially when it comes to microcontrollers, and, as such, I cannot recommend it to anyone who has not had a lot of prior experience. Information may be hard to come by.