Well, you won't find any beaches in Guadalajara, but the city is only a 4½-hour drive (or 5-hour bus ride) from Puerto Vallarta, the hub of the Pacific Coast Resorts. With a little planning, these two very different destinations can be combined into one best-of-both-worlds trip.
Be sure to compare airfares into both cities—depending on where you're flying in from, it might be cheaper to start your journey on the Pacific Coast and work your way inland. If you're driving to PV, the best route is toll Highway 15D to Tepic, followed by Highway 200 (pick it up at the Compostela toll booth).