Hey. I don't know what work or edition of Plato you're trying to read, but if it is straight-Greek with no commentary, that would be very hard.
My first suggestion, I guess, would be to find the syllabi for 1st-3rd semester Greek at your uni, and see how comfortable you are with whatever Greek texts are read.
I don't think Alpha to Omega is all that good. I have heard it does not prepare people for reading Greek, but that may be the fault of unmotivated students or lackluster professors.
You may want to look at Mastronarde (it is boring) or Hansen and Quinn (it is boring)--esp. if they are taught at your uni. Maybe your Greek level is high enough you can easily manage the boring parts of the book and get right to the chapters where you're reading Greek authors.
On beginning Plato, I can offer a couple resources. I am just beginning Greek this summer (reading Mastronarde's text and Croy's), and the goal is to begin reading moderately annotated Plato in January. I have looked at some texts for this (the carrot on the stick). The different texts are geared towards beginning through intermediate audiences, so taking a look at all three may help determine your reading level:
1) Steadman's annotation of Crito: this is HEAVILY annotated. Seems like 60-80% of the words/phrases have glosses or brief explanations. It even glosses the imperfect of 'to be', common demonstratives, etc.! I have only glanced through this, but it looks like it should make Plato more than approachable for those that have finished a first-year textbook. If you mark the glosses that you need, you may figure out what you need to work on (particles or the perfect system or adverbs or what have you). Free ebook!http://geoffreysteadman.com/platos-crito/
2) Greek- A Prose Reading Course, v.2: this is a moderately annotated edition. Significantly less annotated than Steadman, but still a considerable number of glosses. For "post-beginners", and may be of more use if Steadman's has more glosses than you want. It is not free, but still inexpensive (and at some uni libraries). Publisher's Webpage
3) Dyer's Edition of Crito: Annotated edition. Provides glosses and mainly grammatical commentary for words and phrases in considerably more detail than #1 or #2, but also has much greater expectations for the reader's level. But, it is surely the reading level to aim for (and may be useful when reading a passage for the second or third time after using #1 or 2). There are two editions for this--I think
the textkit version has slightly
textkit edition: Apology, Crito, and other Extracts
google books edition: Apology of Socrates and Crito
4) Mastronarde's Apology
Mastronarde has glossed much of the third section of Apology (and some of a speech by Lysias) for classroom use after finishing his textbook. Can be found by scrolling down here: Mastronarde's Resource Page
There is also a very interesting textbook I found for reading the Anabasis from 1888 I found. I may review on textkit once I have advanced more in Mastronarde. If the Anabasis is part of the Greek series at your school, though, leave a note and I'll write a briefer review sooner.