Getting into MYF is not too difficult. Assuming you're asking about VFR options, you have two basic choices: coastal or inland. And the choice will likely be dictated by the weather on the coast and how/where you cross the LA airspace.
Coastal is a bit quicker and much prettier, and would be my first choice if weather allows. Basically, take one of the transition routes to get through LAX airspace, and then follow the coast all the way down to San Diego. Note that you can stay clear of most airspace with appropriate choice of altitude, but talking to socal approach is still a very good idea! When you get down to San Diego, you can stay clear of Miramar's class B through the Torrey Pines area at 3,500 ft (sandwiched between Bravo above and below). And Torrey Pines is a good place for your call-up to MYF tower. From there typically they'll bring you in for a left downwind to 28L. Local knowledge: proceed to Mount Soledad at 3,500, then start your descent and fly to the north-east corner of Mission Bay, where you'll turn to the 45 to the left downwind. Familiarize yourself well with this area on the TAC chart, so you don't accidentally clip Bravo. You'll be close to it. But done right, it works great.
The inland route is pretty much just V186 through the LA and Riverside area and into inland San Diego right over interstate 15. You can duck down under the San Diego class B and get a transition through Ramona's class D if you have to, which will set you up for a long straight-in to MYF (call MYF tower over Gillespie Field or Mount Helix). But the easy way is before you get to the class B just to ask socal approach for class B clearance, direct MYF, and they will almost always give it to you. Take you right over top of Miramar and into Montgomery. Socal will hand you off to MYF over Miramar. And MYF tower will either have you enter a right downwind for 28R, or cross midfield and enter a left downwind for 28L.