Good morning,
I've used a lot of Allegro 4, and never really tried Allegro 5. Right now the biggest learning curve just seems to be getting use to these Events.
I've done a basic Game Loop, I think it's a valid one, but I'm not sure. I'm using the same Game Loops I normally do, checking logic and drawing within the same timer.
1#include <stdio.h>
2#include <allegro5/allegro.h>
3
4int main()
5{
6 // Start Up Allegro
7 al_init();
8
9 // Load Keyboard
10 al_install_keyboard();
11 ALLEGRO_KEYBOARD_STATE Game_Keyboard_State;
12
13 // Create Display
14 ALLEGRO_DISPLAY *Game_Display = NULL;
15
16 Game_Display = al_create_display(640, 480);
17
18 // Create Timer
19 ALLEGRO_TIMER *Game_Timer = NULL;
20 Game_Timer = al_create_timer(1.0 / 60.00f);
21
22 // Create Events
23 ALLEGRO_EVENT_QUEUE *Game_Event_Queue = NULL;
24 Game_Event_Queue = al_create_event_queue();
25
26 // Setup Events
27 al_register_event_source(Game_Event_Queue, al_get_display_event_source(Game_Display));
28 al_register_event_source(Game_Event_Queue, al_get_timer_event_source(Game_Timer));
29 al_register_event_source(Game_Event_Queue, al_get_keyboard_event_source());
30
31 // Start Timer
32 al_start_timer(Game_Timer);
33
34
35 bool Game_Running = true;
36 bool Game_Drawing = true;
37
38 // TEST
39 bool Cycle = false;
40 bool Allow_Flash = false;
41
42 // =================
43 // GAME LOOP - START
44 // =================
45
46 while (Game_Running)
47 {
48 // Draw
49 if (Game_Drawing)
50 {
51 if (Allow_Flash)
52 {
53 if (Cycle)
54 {
55 al_clear_to_color(al_map_rgb(255, 255, 255));
56 Cycle = false;
57 }
58 else
59 {
60 al_clear_to_color(al_map_rgb(0, 0, 0));
61 Cycle = true;
62 }
63
64 al_flip_display();
65 }
66
67 if (!Allow_Flash)
68 {
69 al_clear_to_color(al_map_rgb(255, 0, 0));
70 al_flip_display();
71 }
72
73 Game_Drawing = false;
74 }
75
76 while (1)
77 {
78 // Logic
79 ALLEGRO_EVENT ev;
80 al_wait_for_event(Game_Event_Queue, &ev);
81
82 if (ev.type == ALLEGRO_EVENT_TIMER)
83 {
84 al_get_keyboard_state(&Game_Keyboard_State); // Get Keyboard State
85 if (al_key_down(&Game_Keyboard_State, ALLEGRO_KEY_SPACE))
86 {
87 Allow_Flash = true;
88 }
89 else
90 {
91 Allow_Flash = false;
92 }
93
94
95 Game_Drawing = true;
96 }
97 else if (ev.type == ALLEGRO_EVENT_DISPLAY_CLOSE)
98 {
99 Game_Drawing = false;
100 Game_Running = false;
101 break;
102 }
103
104 if (al_is_event_queue_empty(Game_Event_Queue))
105 {
106 break;
107 }
108 }
109 }
110
111 // =================
112 // GAME LOOP - END
113 // =================
114
115 // Destroy
116 al_destroy_timer(Game_Timer);
117 al_destroy_display(Game_Display);
118 al_destroy_event_queue(Game_Event_Queue);
119
120}
If this doesn't work fully as a valid Game Loop, please let me know what I can do better. I really want to get started with development once again with Allegro! 
I really enjoyed Allegro 4, other than the software rendering.